First-principles study of the atomic and electronic structures of crystalline and amorphous B4C

作者：Ivashchenko V I^*; Shevchenko V I; Turchi P E A

来源：Physical Review B, 2009, 80(23): 235208.

DOI：10.1103/PhysRevB.80.235208

• amorphous state
• band structure
• boron compounds
• crystal structure
• density functional theory
• elastic moduli
• high-pressure effects
• molecular dynamics method
• pseudopotential methods
• total energy

The atomic and electronic structures of crystalline and amorphous B4C were determined within density function theory using the local density approximation and a plane-wave pseudopotential method. For the crystalline phases, chain, and polar structures were considered. The structural parameters were obtained by minimizing the total energy with respect to the size, shape, and internal degrees of freedom of 15 and 45-atom unit cells. The amorphous 120 and 135-atom samples of a-B4C were generated using molecular dynamic simulations in the NVT ensemble using different initial structures. The 120-atom sample was generated from a rhombohedral c-B4C cell, whereas the a-135 sample was obtained from a fcc B4C initial structure that differs essentially from the real crystalline B4C structure. Analysis of the computed results shows that: (i) a random icosahedral network connected with the amorphous B-C matrix is identified in the case of a-B4C; (ii) carbon clusters are observed in the case of the 120-atom sample of an amorphous matrix; (iii) no chain atoms are found in both amorphous samples that can be explained by their bulk moduli that are lower compared to those of their crystalline counterparts; (iv) the chain and polar B4C phases transform into a-B4C under high pressure; and (v) all crystalline structures studied so far are semiconducting, whereas a-B4C is a semimetal.

• 出版日期2009-12