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First-principles study of 6H-AlN under various pressure conditions

Kazuaki Kobayashi and Shojiro Komatsu

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We calculated the electronic and lattice properties of 6H-AlN under various pressure conditions. The pressure conditions are hydrostatic, biaxial, and uniaxial compression and expansion. The 6H polytype has two structures. One is ABCBCB (ABC notation) and the other is ABCACB. 6H-AlN(ABCBCB) is energetically more favorable than 6H-AlN(ABCACB). Symmetry and hexagonality (H[%]) of 6H-AlN(ABCBCB) are P3m1 and 67 %, respectively. The electronic band structures of 6H-AlN polytypes under the ambient pressure show indirect band gaps. The band gap of 6H-AlN(ABCBCB) is closer to direct than that of 6H-AlN(ABCACB). The lattice properties of 6H-AlN(ABCBCB) under the various pressure conditions were optimized automatically by the first-principles molecular dynamics (FPMD) method. We also calculated the electronic band structures, the band gap values, the valence band maximum (VBM), and conduction band minimum (CBM) of 6H-AlN(ABCBCB) under the various pressure conditions. Their electronic band structures are non-metallic and band gaps are indirect with the exception of a few cases. The indirect band gap transforms to direct under expansion conditions.


PACS

71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations

62.50.-p High-pressure effects in solids and liquids

71.15.Mb Density functional theory, local density approximation, gradient and other corrections

71.20.Nr Semiconductor compounds

61.66.Fn Inorganic compounds

Subjects

Condensed matter: electrical, magnetic and optical

Semiconductors

Condensed matter: structural, mechanical & thermal

Dates

Issue 1 (2010)



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