Biography of Saddam Hussein, Dictator of Iraq

Biography of Saddam Hussein, Dictator of Iraq Saddam Hussein (April 28, 1937–December 30, 2006) was the ruthless dictator of Iraq from 1979 until 2003. He was the adversary of the United States during the Persian Gulf War and found himself once again at odds with the U.S. in 2003 during the Iraq War. Captured by U.S. troops, Saddam Hussein was put on trial for crimes against humanity (he killed thousands of his own people) and was ultimately executed on December 30, 2006. Fast Facts: Saddam Hussein Known For: Dictator of Iraq from 1979–2003Also Known As: Saddam Hussein al-Tikriti, The Butcher of BaghdadBorn: April 28, 1937 in Al-Ê ¿Awjah, IraqParents: Hussein Abd al-Majid, Subha Tulfah al-MussallatDied: December 30, 2006  in Baghdad, IraqEducation: High school in Baghdad; law school for three years (did not graduate)Published Works:  Novels including Zabiba and the King, The Fortified Castle, Men and the City, Begone DemonsSpouses: Sajida Talfah, Samira ShahbandarChildren: Uday Hussein, Qusay Hussein, Raghad Hussein, Rana Hussein,Hala HusseinNotable Quote: We are ready to sacrifice our souls, our children, and our families so as not to give up Iraq. We say this so no one will think that America is capable of breaking the will of the Iraqis with its weapons. Early Years Saddam, which means he who confronts, was born in 1937 a village called al-Auja, outside of Tikrit in northern Iraq. Either just before or just after his birth, his father disappeared from his life. Some accounts say that his father was killed; others say he abandoned his family. At almost the same time, Saddams older brother died of cancer. His mothers depression made it impossible for her to care for the young Saddam, and he was sent to live with his uncle Khairullah Tulfah who was briefly imprisoned for political activity. Several years later, Saddams mother remarried a man who was illiterate, immoral, and brutal. Saddam returned to his mother but hated living with his stepfather and as soon as his uncle Khairullah Tulfah (his mothers brother) was released from prison in 1947, Saddam insisted that he go live with his uncle. Saddam didnt start primary school until he moved in with his uncle at age 10. At age 18, Saddam graduated from primary school and applied to military school. Joining the military had been Saddams dream and when he wasnt able to pass the entrance exam, he was devastated. (Though Saddam was never in the military, he frequently wore military-style outfits later in life.) Saddam then moved to Baghdad and started law school, but he found school boring and enjoyed politics more. Saddam Hussein Enters Politics Saddams uncle, an ardent Arab nationalist, introduced him to the world of politics. Iraq, which had been a British colony from the end of World War I until 1932, was bubbling with internal power struggles. One of the groups vying for power was the Baath Party, to which Saddams uncle was a member. In 1957 at age 20, Saddam joined the Baath Party. He started out as a low-ranking member of the Party responsible for leading his schoolmates in rioting. In 1959, however, he was chosen to be a member of an assassination squad. On October 7, 1959, Saddam and others attempted but failed to assassinate the prime minister. Wanted by the Iraqi government, Saddam was forced to flee. He lived in exile in Syria for three months and then moved to Egypt, where he lived for three years. In 1963, the Baath Party successfully overthrew the government and took power, which allowed Saddam to return to Iraq from exile. While home, he married his cousin, Sajida Tulfah. However, the Baath Party was overthrown after only nine months in power and Saddam was arrested in 1964 after another coup attempt. He spent 18 months in prison, where he was tortured before he escaped in July 1966. During the next two years, Saddam became an important leader within the Baath Party. In July 1968, when the Baath Party again gained power, Saddam was made vice president. Over the next decade, Saddam became increasingly powerful. On July 16, 1979, the president of Iraq was forced to resign and Saddam officially took the position. The Dictator of Iraq Saddam Hussein ruled Iraq with a brutal hand, using fear and terror to stay in power. He established a secret police force that suppressed internal dissenters and developed a cult of personality to build public support. His goal was to become the leader of the Arab world, with territory to include the oil fields of the Persian Gulf. Saddam led Iraq in a war against Iran from 1980 to 1988, which ended in a stalemate. Also during the 1980s, Saddam used chemical weapons against Kurds within Iraq, including gassing the Kurdish town of Halabja which killed 5,000 in March 1988. In 1990, Saddam ordered Iraqi troops to take the country of Kuwait. In response, the United States defended Kuwait in the Persian Gulf War. On March 19, 2003, the United States attacked Iraq. Saddam fled Baghdad during the fighting. On December 13, 2003, U.S. forces found him hiding in a hole in al-Dwar, near Tikrit. Death In October 2005, Saddam was tried by the Iraqi High Tribunal on charges of killing the people of the town of Al-Dujay. After a dramatic nine-month trial, he was found guilty of crimes against humanity, including killing and torture, and was sentenced to death. On December 30, 2006, Saddam Hussein was executed by hanging; his body was later removed to a secret location. Legacy The actions of Saddam Hussein have had a powerful impact on international politics for the 21st century. Americas relationship with Iraq and other nations of the Middle East were strongly influenced by the conflicts with Saddams Iraq. The fall of Saddam in 2003 was pictured around the world with images of his statue being pulled down by cheering Iraqis. Since Saddams fall, however, a number of challenges made life in Iraq extraordinarily difficult; employment remains low, and the rise of Al Qaeda and the Islamic State (ISIS) led to violence. Sources: The Editors of Encyclopaedia Britannica. â€Å"Saddam Hussein.†Ã‚  Encyclopà ¦dia Britannica, 18 Jan. 2019.â€Å"Saddam Hussein Biography.†Ã‚  Encyclopedia of World Biography, Advameg, Inc.Saddam Caught Like a Rat in a Hole.  CNN.com, 15 December 2003.â€Å"Saddam Hussein Biography.†Ã‚  Encyclopedia of World Biography.

Cómo puede un extranjero divorciarse en Estados Unidos

Cà ³mo puede un extranjero divorciarse en Estados Unidos  ¿Pueden  divorciarse todos los extranjeros que residen en los Estados Unidos con independencia de su estatus migratorio y sin que importe el paà ­s en el que se casaron? Para evitar problemas es conveniente conocer los puntos bsicos que se explican a continuacià ³n, asà ­ como cules son los problemas migratorios que pueden surgir por un divorcio y, por à ºltimo, quà © debe hacerse para que un divorcio en Estados Unidos tenga efectos legales en el paà ­s de origen. En el caso de desconocer dà ³nde se encuentra la persona de la que se quiere divorcia, es posible buscarlo en varias bases de datos oficiales de Estados Unidos. La importancia del estado a la hora de divorciarse en Estados Unidos En Estados Unidos, los asuntos de matrimonio y divorcio son competencia de los estados. Esto significa que las reglas pueden variar de uno a otro. Sin embargo, en todos los estados van a pedir que se cumplan al menos dos requisitos.   En primer lugar, que se pruebe la identidad de la persona que solicita el divorcio. Cada estado tiene un listado con todos los documentos que se admiten, como  la licencia de manejar, la tarjeta de residencia permanente, el pasaporte o la matrà ­cula consular. En segundo lugar, excepto en los casos de Alaska y Washington, se pide que la persona que se quiere divorciar pueda probar que reside en el estado en el que solicita el divorcio. En este punto las reglas varà ­an enormemente. Por ejemplo, en Dakota del Sur es suficiente probar que se vive en ese estado en el momento de iniciar los trmites. Pero ese es un caso excepcional, ya que la mayorà ­a de los estados piden probar residencia por 90 dà ­as, 180 dà ­as o, incluso, un aà ±o. Entre los estados que exigen residencia por ms de 352 dà ­as se encuentran Connecticut, Iowa, Maryland, Massachusetts, Nebraska, Nuevo Hampshire, Nueva Jersey, Nueva York, Rhode Island y Virginia Occidental. Algunos estados, adems, piden un mà ­nimo de tiempo de residencia en el condado en el que se presentan los papeles. Por ejemplo, en California se exigen 180 dà ­as de residencia en el estado, de los cuales 90 tienen que ser en el condado en el que se solicita el fin del matrimonio. El estado en el que una persona se divorcia es importante por varias razones. En primer lugar, porque cada estado regula las causas por las que es posible solicitarlo. En Estados Unidos dos de cada tres estados permiten lo que se conoce como no-fault divorce,  es decir, querer divorciarse es razà ³n suficiente para solicitarlo y obtenerlo. En los otros estados hay que cumplir con alguno de los requisitos que se refieren al incumplimiento del acuerdo matrimonial por alguno de los dos cà ³nyuges. En segundo lugar, los estados pueden exigir que se notifique a la otra parte el inicio del procedimiento de divorcio en lo que se conoce en inglà ©s como service of process. Se pueden admitir diferentes formas para realizar la notificacià ³n, pero en el caso de personas con un cà ³nyuge fuera de los Estados Unidos este requisito puede ser, en ocasiones, difà ­cil de cumplir, pero no por ello puede ignorarse. Y, en tercer lugar, las leyes del estado en el que se dicta el divorcio van a decidir sobre aspectos como divisià ³n de las propiedades, si las hay, custodias de hijos, y pensiones de alimentos o de sostenimiento (conocidas en inglà ©s como child support y alimony, respectivamente). Efectos migratorios del divorcio Cualquier persona que reside habitualmente en Estados Unidos puede divorciarse, cumpliendo con los requisitos del estado en el que solicita el divorcio. El procedimiento tiene lugar en la corte civil y depende del estado. Esos datos no se comunican con inmigracià ³n. Sin embargo, un divorcio sà ­Ã‚  puede tener consecuencias migratorias en tres casos: 1. En primer lugar, las personas que obtuvieron una tarjeta de residencia por matrimonio y se divorcian podrà ­an perderla, dependiendo del momento y de las circunstancias de la finalizacià ³n del và ­nculo matrimonial. Aunque la situacià ³n es ms delicada para las personas que desean divorciarse antes de levantar la condicionalidad de su green card, lo cierto es que los efectos pueden darse incluso cuando ya se tiene la tarjeta de residencia definitiva. El  problema aparece cuando se solicita la ciudadanà ­a por naturalizacià ³n y ya consta el estado civil como divorciado. 2. En el caso de divorcio en el que la pareja tiene hijos en comà ºn, puede establecer una pensià ³n de mantenimiento para los menores. En el caso de incumplirse el pago de la pensià ³n de alimentos puede haber consecuencias civiles, penales y tambià ©n migratorias que pueden ir desde multas, penas de prisià ³n y anulacià ³n del pasaporte, hasta negacià ³n de beneficios migratorios como la tarjeta de residencia o la ciudadanà ­a estadounidense por naturalizacià ³n. 3. En tercer lugar y con aplicacià ³n para todas las personas extranjeras en Estados Unidos, los casos de bigamia son causa de deportacià ³n y de denegacià ³n de la adquisicià ³n de la ciudadanà ­a estadounidense por naturalizacià ³n. La bigamia se produce cuando una persona est casada con otras dos al mismo tiempo. Por esta razà ³n conviene pensar bien el casarse en Estados Unidos sin antes divorciarse pensando que las autoridades estadounidenses nunca se van a enterar si hubo o no matrimonio previo en otro paà ­s. En estos casos, muchas veces se enteran por denuncias anà ³nimas que crean problemas migratorios que son difà ­ciles o imposible de resolver, y no es posible pedir un waiver. Adems, hay el agravante de que si hay una condena por bigamia se anulan todos los beneficios migratorios obtenidos a partir del momento en que se produjo la bigamia. Quà © hacer para que el divorcio en EEUU tenga efectos legales en el paà ­s de origen Las personas extranjeras pueden divorciarse en Estados Unidos, sin embargo, eso no quiere decir que ese divorcio es vlido en sus paà ­ses de origen o que produzca efectos legales automticamente. De hecho, existen dos formas completamente diferentes sobre cà ³mo otros  paà ­ses pueden contemplar un divorcio de uno de sus nacionales obtenidos en Estados Unidos. En primer lugar, se encuentran aquellos paà ­ses que no le reconocen ningà ºn valor legal y exigen que sus connacionales se divorcien en el paà ­s de origen, en persona o a travà ©s de un representante legal. Es, por ejemplo, el caso de Mà ©xico Asà ­, si un mexicano se casa en Mà ©xico pero vive  habitualmente en Estados Unidos, debe divorciase en su paà ­s. Si no quiere o no puede viajar a Mà ©xico, puede firmar un poder notarial a favor de un abogado o de una persona de confianza para que le represente en Mà ©xico durante los trmites de divorcio. Para realizar esos trmites puede cerrarse una cita con Mexitel. Tambià ©n existe un grupo de paà ­ses que sà ­ reconocen el valor legal de un divorcio obtenido por sus nacionales en Estados Unidos. Sin embargo, para que produzca efectos legales se exige que se lleve a cabo un trmite adicional para registrar dicho divorcio. Como ejemplo puede citarse el caso de los colombianos, ya que en Colombia se reconoce la validez de un divorcio dictado en Estados Unidos, imponià ©ndose solo la obligacià ³n de realizar lo que se conoce como exequtor ante la Sala Civil de la Corte Suprema. Solo se puede solicitar cuando la sentencia es final y ya no caben apelaciones o peticiones de nulidad. Adems, el requisito del exequtor tambià ©n rige para otros paà ­ses, por ejemplo, Perà º. Otros paà ­ses que tambià ©n optan por reconocer la validez del divorcio que sus connacionales obtienen en Estados Unidos piden diferentes trmites. Por ejemplo, Argentina da la opcià ³n de registrar y dar publicidad al divorcio dictado en Estados Unidos mediante su inscripcià ³n en el Registro Nacional de Estado y Capacidad mediante un procedimiento judicial o uno consular. Debido a que las reglas cambian segà ºn el paà ­s, lo recomendable es que cada migrante consulte con su embajada para determinar cules son los pasos a seguir y antes de proceder a obtener la apostilla de la Haya en el documento de divorcio, informarse sobre si ese trmite es necesario, ya que no es barato. Este es un artà ­culo informativo. No es asesorà ­a legal.

Behavior modification for children with ADHD Essay

Behavior modification for children with ADHD - Essay Example This is a significant number that makes ADHD one of the most common learning and behavioral disorders to date. The number of American children and adults diagnosed with ADHD has significantly increased from over the years (Frame, 2003). ADHD is a medical term and as it is a problem related to children, that educators and researchers in education should learn its explanation and the symptoms that help identify the problem. It is necessary to clarify the term ADHD because it is not a single behavior but a mix of complex patterns that it is sometimes called an â€Å"assemblage† (Marcus &Saka, 2006 cited in Goodwin, 2010, p.2). It is a condition that the National Institute of Mental Health (2012) explains as â€Å"one of the most common childhood brain disorders and can continue through adolescence and adulthood† (p.1). The most obvious symptoms are â€Å"difficulty staying focused and paying attention, difficulty controlling behavior, and hyperactivity (over-activity). These symptoms can make it difficult for a child with ADHD to succeed in school, get along with other children or adults, or finish tasks at home† (ibid, p.1). In order to be diagnosed, symptoms include inattentiveness, disruptivene ss, as well as social and academic discrepancies in the child’s school or home settings. For example, this includes poor interactions with their parents, teachers, and classmates and a decrease in academic achievement. Children with ADHD endure these difficulties chronically and persist into adolescence and adulthood, negatively impacting their lives and the people surrounding them (Jones & Chronis-Tuscano, 2008). Many children are losing their battle with ADHD without the much needed help from their surroundings. ADHD cannot be categorized as a medical problem, but it is a behavioral and learning difficulty that needs to be effectively managed in the classroom by teachers and at home by the parents, because â€Å"there is currently no cure

Human skeleton. What kinds of information can human skeletons give us Essay

Human skeleton. What kinds of information can human skeletons give us about past lifestyles - Essay Example To effectively study the past human lifestyle, archeologists examine human remains of ancient societies and this where the human skeletons comes handy. Such human materials such as the skeletons, food remains, wrecks of buildings, and human artifacts help the archeologists to rebuild the human past lifestyle. All the information recorded about the human materials such as the human skeletons are referred to as archeological records. These records comprise of all the humans occupying the areas of interest and the remains of human material in those areas. These records are used for study through laboratory examinations of the materials and excavations and field studies. Archeologists have to excavate human graveyards and get the human skeleton to their study stations for the development of their research on the human past lifestyle. The skeletons excavated are an important source of information about the human past lifestyle. The previous and medieval burials are generally unspecified. However, they give important information on average human being that is otherwise uncommon in historical findings. They are in information about the past beliefs, handling of the dead and ritual behavior. Skeletons can provide relevant kinds of information for one to study the past human lifestyle. As a result of this fact, the archeologists have to first of all examine the physical vestiges of real people. Study of the human skeleton gives a new dimension of the human past life such as their health, and the form of their population which constitutes to their lifestyle. To study the past human lifestyle, the fundamental requirements by the archeologists include; the sex and age composition of the population, the ailments of the past, the common strains and stresses of daily life, and the appearance and physical size. Skeletons help archeologists in their study about the past human life by giving hints or actual age information about the fossils. It is not a reliable and valid method to determine age just by the size of the skeleton. Skeletons can give age information by studying the trimmings of long bones and other sections of the bones separated in the children’s skeleton. The detachments give room for the bone to grow. The separated bones, called epiphyses, all combine at distinct ages. The phase of bones combining is used by the archeologists to age an adolescent. Skeletons also provide the relevant information on age by studying the teeth system. Permanent molar grows at the age of six. However, studying the ageing skeletons to give age information is more challenging. Such information provided by the skeletons is helpful in providing information on the different diets eaten by the people in the past. From a closer look of the tooth wear in the skeletons, one can understand the kinds of foods by the past people and this closely gives the researcher the lifestyle lived by the past people. The archeologists then classify the skeletons into three pre- established categories namely; old, middle age, and young. Such information is vital in studying the different past human lifestyle according to the various age class that existed in the past age class. Another important type of information the human skeleton can provide for a comprehensive study of the past human lifestyle is the information on sex. It is challenging to use the skeletons to determine the sex of a child that had not reached the puberty stage. To easily determine the sex of an adult, archeologists look at the pelvis having in mind that, women have bowl-shaped and wide pelvis while that of men is narrow and tall. By looking at such differences in the skeletons, relevant informat

Electronic Structure and Spontaneous Polarization in BiFeO3

Electronic Structure and Spontaneous Polarization in BiFeO3 Electronic structure and spontaneous polarization in multiferroic bulk BiFeO3 Z. Mahhouti 1,2,3,* , H. El Moussaoui 1 , M. Hamedoun 1 , M. El Marssi 3 , A. Lahmar 2 , A. El Kenz 2 , and A. Benyoussef 1,2,4 Abstract: The electronic structure, magnetic properties and spontaneous polarization in Bismuth ferrite BiFeO3 are investigated using first-principle calculations. The computed results show that the ground state of bulk BiFeO3 is rhombohedral R3c symmetry with G-type antiferromagnetic ordering and insulating, the computed results are in good agreement with available experiments. The electronic structure has been studied using the full potential linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation (GGA) and modified Becke-Johnson potential (mBJ). Therefore, the finding band gap value is equal to the experimental value (Eg=2.5 eV) and much better than other theoretical values, the local magnetic moment at the Fe atoms reaches the experimental value and it is in good agreement with previously reported theoretical, with the large atomic displacement the modern theory of polarization predicts a large spontaneous polarization in multiferroic bulk BiFeO3. INTRODUCTION The multiferroic term denotes the coexistence of several ferroic orders (ferroelectric, ferromagnetic, and ferroelastic) in one material[1], coupled or not. Multiferroic materials are very rare because the origins of ferroelectricity and ferromagnetism are hardly compatible as shown by Hill et al.[2][3]. However, there are some exceptions such as La0.1Bi0.9MnO3 which is ferroelectric below 770 K and ferromagnetic below 105 K[4]. The definition of multiferroic has therefore been extended to materials with antiferroic orders such as BiFeO3 which is ferroelectric and antiferromagnetic.      Ã‚   Bismuth ferrite BiFeO3 (BFO) is one of the few magnetoelectric multiferroics who has simultaneously ferroelectric and antiferromagnetic orders under ambient conditions of temperature and pressure. Indeed, its high Curie temperature (TC = 1103 K)[5] and Nà ©el temperature (TN = 643 K)[6] provide a wide range of applications at different temperatures[7] such as spintronics, data storage and microelectronic devices[8][9], In addition, a magnetoelectric coupling is possible at room temperature. Recently, BFO has seen a considerable increase in interest since the discovery of a much better spontaneous polarization, greater than 150  µC/cm2, when the material is grown in thin layers[10]. This discovery aroused great enthusiasm among the scientific community who wanted to explain the origin of some phenomenon and explore this material again. The phase diagram established according to the reference[11] shows the succession of three phases with increasing of temperature denoted à ¯Ã‚ Ã‚ ¡, à ¯Ã‚ Ã‚ ¢,and à ¯Ã‚ Ã‚ §, respectively. In its bulk form and at room temperature, BFO has a distorted perovskite structure with rhombohedral symmetry and space group R3c (a = b = c = 5.63 Ã…, à ¯Ã‚ Ã‚ ¡ = 59.4 °)[12][8]. The primitive unit cell contains two formula units (ten atoms), each Fe atom is surrounded by six antiparallel spin neighbors, the magnetic moments are oriented perpendicularly to the [111] direction, which leads to develop a G-type antiferromagnetic order on the whole of the material. However, new observations have revealed that the direction in which antiferromagnetism manifests rotates through the crystal[13]. This noncollinearity propagates within the material with a period from 620 Ã… to 640 Ã…[13][14] and superimposes on the G-type antiferromagnetic order. As the noncollinearity is quite minimal , the simplification to a collinear magnetic structure is possible[15]. In this paper, the noncollinearity effects were not taken during our calculations. Since BFO is grown as a thin layers, the material may undergo a compressive or extensive stress due to the difference between the primitive cell of the material in its bulk form and those of the monocrystalline substrate, the small grown thickness is able to accept any relaxation of the structure. This can cause changes in the structure parameters of the crystal compared to its bulk form. However, other experimental works[16][17] showed that even BFO grown in thin layers, retains its rhombohedral symmetry. For a long time BFO considered too low to be exploitable ( Ps = 6.1  µC/cm2 ) according to the first measurements of Teague et al.[5], the ferroelectricity of BFO was studied again following the results of Young et al.[10] on thin layers of BFO ( Ps = 158  µC/cm2). However, many experimental studies carried out during this period gave a confusing results, the spontaneous polarization varying from 2.2  µC/cm2 [18] to 158  µC/cm2 [10]. The study of the ferroelectricity of BFO is a concrete example to combine experimental results and theoretical calculations. In this case, the calculation methods allow to explain the difference between the first measured values of bulk BFO and those obtained on the same material grown in thin layers. In this paper, we study in detail the magnetic properties of bulk BFO, while considering a G-type antiferromagnetic order. But it is necessary to determine first the electronic configuration and to calculate the band gap, in order to understand and obtain the theoretical model which corresponds to the reality of the material, and then to determine the spontaneous polarization using modern theory of polarization. METHOD The calculations which we present in the remainder of this paper use the density functional theory (DFT) implemented in WIEN2k code. The interactions between electrons and ions are described in the framework of full potential linearized augmented plane wave (FP-LAPW) method. As the 3d electrons in transition -metal Fe atom are incompletely filled, the spin density approximation was employed withinstry the Perdew-Burke-Ernzerhof (PBE) form of the generalized gradient approximation (GGA) and modified Becke-Johnson potential (mBJ). The new version of the exchange potential, proposed for the first time by the Becke and Johnson[19], was recently published by Tran and Blaha[20]. The modified Becke-Johnson potential (mBJ) proposed by Tran and Blaha is: With is the electronic density, is kinetic energy density and is the potential of Becke-Roussel. In this work, the mBJ potential is used in combination with the GGA-PBE approximation to compute the electronic structure, magnetic properties and spontaneous polarization in multiferroic bulk BFO. Our calculations do not include the spin-orbit interactions and the noncollinearity effects. The mesh of the first Brillouin zone in the reciprocal space was carried out using a 4 x 4 x 4 Monkhorst-Pack k-points grid. The structural parameters of BFO in space group R3c ( i.e, the lattice constant and atomic positions ) are considered as calculated by Wang et al.[8] as given from Kubel et al.[12]. The results of relaxing the cell volume, rhombohedral angle, and atomic positions within the R3c symmetry in reference[8] show that there is an alternation of Bi3+ and Fe3+ ions along the [111] axis; Each of these atoms is surrounded by six oxygen atoms, which thus form an octahedron around each cat ion. Inside the octahedron FeO6, the Fe3+ ion is outside the FeO2 plane (forming the base of the octahedron), which leads a distortion of the octahedron. The calculation of the spontaneous polarization using the modern theory of polarization is carried out by determining the difference in polarization between two symmetry (The non-centrosymmetric phase R3c which is ferroelectric and the centrosymmetric phase R-3c supposed paraelectric). In order to evaluate the polarization of the structure studied, we must therefore use a structure (centrosymmetric) as a reference with the same unit cell as the real structure (non-centrosymmetric), but its atomic positions do not induce electrical dipoles. Energetically, these two structures are very close, which confirms our choice of R-3c symmetry as a centrosymmetric reference. They differ by the addition of a center of inversion within the symmetry, and the passage from one symmetry to the other is due to the displacement of the atoms along the [111] direction which is accompanied with a rotation of the FeO6 octahedra perpendicular to the same direction. This evolution of the paraelectric phase t o the ferroelectric phase allows us to explain the birth of ferroelectricity within the bismuth ferrite BFO and to reproduce it efficiently in our calculations. The modern theory of polarization was applied for the first time to compute the ferroelectricity within the cubic perovskite-type KNbO3. The results obtained ( à ¯Ã‚ Ã¢â‚¬Å¾P = 35  µC/cm2 [21][22]) showed excellent agreement with the experimental data ( à ¯Ã‚ Ã¢â‚¬Å¾P = 37  µC/cm2[23]). Other studies were carried out subsequently, confirming the reliability of this method with respect to the experimental reality. Today, the modern theory of polarization is widely used. Results and Discussion Electronic and magnetic properties In this section, we study the electronic structure of bulk BFO in ferroelectric R3c structure, considering the relaxing values of cell parameter, rhombohedral angle and atomic positions by Wang et al.[8]. We computed and plotted the band structure and electronic state densities with the same parameters mentioned at the paragraph II. The band gap value are calculated using mBJ potential in combination with the GGA-PBE approximation, our calculated band gap value is the same as the value measured by Gao et al.[24] from the UV-visible diffuse reflectance spectrum witch is equal to 2.5 eV, our computed band gap is much better than other theoretical works such as Neaton et al.[15] who found an indirect band gap of 0.4, 1.3, and 1.9 eV using LSDA+U approximation with U=0, 2, and 4 eV, respectively. The same for Tà ¼tà ¼ncà ¼ et al.[25] they found an indirect band gap of 0.9, 1.4, and 2.1 eV using LSDA+U approximation with U=0, 2, and 4 eV, respectively. Our band structure results (Fig.1 ) indicate an indirect band gap of approximately 2.5 eV witch is in excellent agreement to the experimental measurement of about 2.5 eV [24][26]. Therefore, this equality between our calculated band gap and the experimental value confirms the insulating character of bulk BFO. In order to understand why the magnetic moments of the Fe atoms were arranged antiparallel within bulk BFO, we relaxed it according to different magnetic configurations: paramagnetic, ferromagnetic, and antiferromagnetic. The ground-state energy of the various possible magnetic configurations shows that the G-type antiferromagnetic configuration is the one which offers the material its greatest stability. FIG. 1. Calculated band structure for rhombohedral BiFeO3. FIG. 2. Calculated total density of states for rhombohedral BiFeO3. Calculated density of state (Fig.2) for R3c BFO indicates an identical distribution between electronic states up and down, which clearly exhibits the antiferromagnetic order of the material, in this case the antiferromagnetic order can only be G-type. The Fe atoms along the [111] axis have a local magnetic moment of 4.02 ÃŽÂ ¼B comes from 3d states, this value is much better than 4.25 ÃŽÂ ¼B and 4.17 ÃŽÂ ¼B reported by Tà ¼tà ¼ncà ¼ et al.[25] using LSDA+U with U = 4 and 6 eV, respectively. Therefore, our computed local magnetic moment of Fe atoms is very close to the measurement value of about 3.75ÃŽÂ ¼B [27]. FIG. 3. Atomic projection of electronic PDOS for rhombohedral BiFeO3. Figure 3 shows atomic projected electronic density of states (PDOS) around the ban gap region for both spin channels. The results suggest that the valence band are predominantly formed by Fe 3d states, hybridized with a contribution from O 2p states. Conduction band states are occupied by a large amount of Fe 3d states, hybridized with a small contribution of Bi 6p states that also contains a significant amount of O 2p states. Spontaneous polarization The spontaneous polarization was calculated within bulk BFO using the ferroelectric structure R3c and the hypothetical centrosymmetric phase R-3c. The centrosymmetric phase must be judiciously chosen, in order to found the difference of ferroelectric polarization between the centrosymmetric and non-centrosymmetric phases less than the quantum of polarization, Where is the electronic charge, is a lattice vector in the direction of polarization, and is the volume of the unit cell. Our calculations have shown that centrosymmetric phase R-3c is the structure closest to the ferroelectric structure R3c, both energetically as well as structural. This symmetry differs from the R3c only by the addition of a center of inversion. The transition from the paraelectric to the ferroelectric phase was characterized by a large displacement of the atoms along the [111] axis and a rotation of the FeO6 octahedra. Therefore, we expect that the spontaneous polarization develops along the [111] axis. In order to calculate the difference of polarization, we have considered that the transition from paraelectric to ferroelectric phase was done adiabatically and continuously. In this way, each atom moves along a path divided into segments of equal length. This method allowed us to follow the evolution of the spontaneous polarization during the whole paraelectric-ferroelectric transition. Throughout the paraelectric-ferroelectric transition, it is imperative to avoid any external contribution to symmetry, such as compression or expansion of the unit cell (in this case we do not calculate the real spontaneous polarization). For this reason, the structures used for our calculations have the same cell parameters, only the atomic positions were shifted. The modern theory of polarization compute the both, ionic and electronic contribution to the spontaneous polarization using the sum of the Wannier centers of the occupied bands. Our results showed that the spontaneous polarization developed along three directions, and was 58.8  µC/cm2 along each axis, resulting a spontaneous polarization of 101.1  µC/cm2 along the [111] axis which is in full agreement with the spontaneous polarization calculated by Neaton et al.[15] using LSDA+U. Early measurements on bulk BFO single crystals[5] found a small polarization of about 6.1  µC/cm2. On the other hand, many experiment studies on thin film samples of BFO showed a large spontaneous polarization of about 100-158  µC/cm2 [16][10]. The anomalously early value was caused by several explanations. First, the authors[5] indicated that their hysteresis loops were not saturated. Second, maybe the small value limited by the poor of the sample quality. Finally, the third explanation is that the crystal structure is not the same. Recently, Lebeugle et al.[28] have prepared a highly pure BFO single crystal (bulk BFO with a rhombohedral R3c symmetry) and measured the spontaneous polarization, they found a very large value of about 100  µC/cm2 [28] which is an intrinsic property of the bulk BFO, as expected by our theoretical studies. CONCLUSIONS In summary, Bismuth ferrite BiFeO3 is one of a few magnetoelectric multiferroics who has simultaneously ferroelectric and ferromagnetic orders, it has seen a considerable increase in interest since the discovery of a high spontaneous polarization. The first principle calculations with our approximations and parameters chosen allowed us to understand and obtain the behaviors of electronic and magnetic properties which make possible the computing of the right band gap and local magnetic moment. The property intrinsic of the large spontaneous electric polarization in bulk BiFe2O3 showed by recently experiment studies was confirmed by our theoretical investigations using the modern theory of polarization. These good agreements between our theoretical investigation and experimental measurement allow the scientific community to compute other properties and understand the physics behind the measurement at the atomic level. References [1]H. Schmid, Multi-ferroic magnetoelectrics, Ferroelectrics, vol. 162, no. 1, pp. 317-338, Jan. 1994. [2]N. A. Hill, Why Are There so Few Magnetic Ferroelectrics?, J. Phys. Chem. B, vol. 104, no. 29, pp. 6694-6709, Jul. 2000. [3]N. A. Hill, Density Functional Studies of Multiferroic Magnetoelectrics, Annu. Rev. Mater. Res., vol. 32, no. 1, pp. 1-37, Aug. 2002. [4]A. Moreira dos Santos et al., Orbital ordering as the determinant for ferromagnetism in biferroic BiMnO 3, Phys. Rev. B, vol. 66, no. 6, Aug. 2002. [5]J. R. Teague, R. Gerson, and W. J. James, Dielectric hysteresis in single crystal BiFeO3, Solid State Commun., vol. 8, no. 13, pp. 1073-1074, 1970. [6]G. A. Smolenskii and I. E. Chupis, Ferroelectromagnets, Phys.-Uspekhi, vol. 25, no. 7, pp. 475-493, Jul. 1982. [7]M. Fiebig, Revival of the magnetoelectric effect, J. Phys. Appl. Phys., vol. 38, no. 8, pp. R123-R152, Apr. 2005. [8]J. Wang, Epitaxial BiFeO3 Multiferroic Thin Film Heterostructures, Science, vol. 299, no. 5613, pp. 1719-1722, Mar. 2003. [9]Y. Tokura, MATERIALS SCIENCE: Multiferroics as Quantum Electromagnets, Science, vol. 312, no. 5779, pp. 1481-1482, Jun. 2006. [10]K. Y. Yun, D. Ricinschi, T. Kanashima, M. Noda, and M. Okuyama, Giant ferroelectric polarization beyond 150 ÃŽÂ ¼C/cm2 in BiFeO3 thin film, Jpn. J. Appl. Phys., vol. 43, no. 5A, p. L647, 2004. [11]R. Palai et al., ÃŽÂ ² phase and ÃŽÂ ³ ˆ’ ÃŽÂ ² metal-insulator transition in multiferroic Bi Fe O 3, Phys. Rev. B, vol. 77, no. 1, Jan. 2008. [12]F. Kubel and H. Schmid, Structure of a ferroelectric and ferroelastic monodomain crystal of the perovskite BiFeO3, Acta Crystallogr. B, vol. 46, no. 6, pp. 698-702, Dec. 1990. [13]I. Sosnowska, T. P. Neumaier, and E. Steichele, Spiral magnetic ordering in bismuth ferrite, J. Phys. C Solid State Phys., vol. 15, no. 23, p. 4835, 1982. [14]D. Lebeugle, D. Colson, A. Forget, M. Viret, A. M. Bataille, and A. Gukasov, Electric-Field-Induced Spin Flop in BiFeO 3 Single Crystals at Room Temperature, Phys. Rev. Lett., vol. 100, no. 22, Jun. 2008. [15]J. B. Neaton, C. Ederer, U. V. Waghmare, N. A. Spaldin, and K. M. Rabe, First-principles study of spontaneous polarization in multiferroic Bi Fe O 3, Phys. Rev. B, vol. 71, no. 1, Jan. 2005. [16]J. Li et al., Dramatically enhanced polarization in (001), (101), and (111) BiFeO3 thin films due to epitiaxial-induced transitions, Appl. Phys. Lett., vol. 84, no. 25, pp. 5261-5263, Jun. 2004. [17]G. Xu, H. Hiraka, G. Shirane, J. Li, J. Wang, and D. Viehland, Low symmetry phase in (001) BiFeO3 epitaxial constrained thin films, Appl. Phys. Lett., vol. 86, no. 18, p. 182905, May 2005. [18]V. R. Palkar, J. John, and R. Pinto, Observation of saturated polarization and dielectric anomaly in magnetoelectric BiFeO3 thin films, Appl. Phys. Lett., vol. 80, no. 9, pp. 1628-1630, Mar. 2002. [19]A. D. Becke and E. R. Johnson, A simple effective potential for exchange, J. Chem. Phys., vol. 124, no. 22, p. 221101, Jun. 2006. [20]F. Tran and P. Blaha, Accurate Band Gaps of Semiconductors and Insulators with a Semilocal Exchange-Correlation Potential, Phys. Rev. Lett., vol. 102, no. 22, Jun. 2009. [21]R. Resta, M. Posternak, and A. Baldereschi, Towards a quantum theory of polarization in ferroelectrics: The case of KNbO 3, Phys. Rev. Lett., vol. 70, no. 7, p. 1010, 1993. [22]R. Resta, M. Posternak, and A. Baldereschi, First-Principles Theory of Polarization in Ferroelectrics, in MRS Proceedings, 1992, vol. 291, p. 647. [23]W. Kleemann, F. J. Schà ¤fer, and M. D. Fontana, Crystal optical studies of spontaneous and precursor polarization in KNbO 3, Phys. Rev. B, vol. 30, no. 3, p. 1148, 1984. [24]F. Gao et al., Preparation and photoabsorption characterization of BiFeO3 nanowires, Appl. Phys. Lett., vol. 89, no. 10, p. 102506, Sep. 2006. [25]H. M. Tà ¼tà ¼ncà ¼ and G. P. Srivastava, Electronic structure and zone-center phonon modes in multiferroic bulk BiFeO3, J. Appl. Phys., vol. 103, no. 8, p. 083712, Apr. 2008. [26]T. Kanai, S. Ohkoshi, and K. Hashimoto, Magnetic, electric, and optical functionalities of (PLZT) x (BiFeO 3) 1- x ferroelectric-ferromagnetic thin films, J. Phys. Chem. Solids, vol. 64, no. 3, pp. 391-397, 2003. [27]I. Sosnowska, W. Schà ¤fer, W. Kockelmann, K. H. Andersen, and I. O. Troyanchuk, Crystal structure and spiral magnetic ordering of BiFeO 3 doped with manganese, Appl. Phys. Mater. Sci. Process., vol. 74, no. 0, pp. s1040-s1042, Dec. 2002. [28]D. Lebeugle, D. Colson, A. Forget, and M. Viret, Very large spontaneous electric polarization in BiFeO3 single crystals at room temperature and its evolution under cycling fields, Appl. Phys. Lett., vol. 91, no. 2, p. 022907, Jul. 2007.

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