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Electronic structure of AlP under pressure

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 احمد محمود عبد اللطيف الخفاجي 5/28/2011 9:59:05 AM
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 The effect of pressure on the structural and electronic parameters of zinc-blende aluminum phosphide crystal has been investigated using the large unit cell within the framework of complete neglect of differential overlap and the linear combination of atomic orbital approximation. Cohesive energy, indirect band gap, valence bandwidth, conduction bandwidth, bulk modulus, and valence charge distribution are all obtained. The calculations show a good agreement of lattice constant, cohesive energy, valence bandwidth, and bulk modulus with the experimental data. Whereas, the calculated band gap is twice the experimental value. That is what we expect from Hartree-Fock method. Band gap shows a good trend compared to theoretical values. The effect of pressure on the aforementioned properties is investigated. It is found that the indirect band gap, valence bandwidth, bulk modulus and cohesive energy increase with increasing pressure, while the conduction bandwidth decreases. The maximum value of pressure is taken to be 9 GPa, because beyond this value, the phase of AlP transforms from zinc blende phase to nickel arsenic phase. Aluminum phosphide (AlP) is a wide-indirect band gap semiconductor. At normalconditions,   AlPcrystallizes in the zinc-blende (zb) structure [1]. High-pressure experiments on  this compound are difficult because of sample handling problems; AlP is unstable in air [2].  The zb  form has been reported theoretically to be metastable. The zinc- blende phase is  known to transform to the nickel arsenic (NiAs) phase at about ((17 – 9.5 GPa [3]. Although other studies have placed this transformation at a somewhat smaller pressure (7- 9.3) GPa [4]. At a pressure of about 36 GPa the NiAs phase has been reported to undergo a Cmcm–like distortion with no significant change in volume. The CsCl phase is a possible candidate for AlP at very high pressures [2]. AlP is a subject of extensive theoretical studies ranging from the semiempirical to the first principles methods [5] within the density functional theory (DFT) framework using both pseudopotential [2], and all-electron approaches. For the bulk phase of AlP, theoretical calculations based on the Hartree-Fock [6], and potential model [7] have obtained a very good description of its structural and electronic properties.

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  • Electronic structure pressure

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