Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, People's Republic of China.
J Phys Condens Matter. 2010 Aug 11;22(31):315503. doi: 10.1088/0953-8984/22/31/315503. Epub 2010 Jul 16.
Using first-principles calculations, the structural, mechanical and electronic properties of the experimentally synthesized B(12)-based ternary crystals (AlMgB(14), AlNaB(14), AlLiB(14), Mg(2)B(14), MgSi(2)B(12), MgC(2)B(12), Li(2)Si(2)B(12) and Li(2)C(2)B(12)) have been investigated. The theoretical equilibrium lattice constants of these crystals agree with the experimental values. The Vickers hardness (H(v)) estimated from the theoretical Young's moduli ranges from 20 to 30 GPa, and the MgC(2)B(12) compound (H(v) = 31.4 GPa) is harder than α-boron. Based on the electron density of states and Mulliken population analysis, the origination of hardness and interaction between the interstitial atoms and the B(12) framework were discussed. Scaled bond order of the B-B bonds was used to interpret the hardness of these B(12)-based ternary compounds. The crystal hardness is primarily determined by the B(12) icosahedral skeleton, whereas the contributions of metal atoms manifest as the electron transfer from metal to B atoms. We also calculated the ideal tensile strength of AlMgB(14) and MgC(2)B(12) and found that the <001> and <010> directions are their cleavage directions under tensile strains, respectively.
采用第一性原理计算研究了实验合成的基于 B(12)的三元晶体（AlMgB(14)、AlNaB(14)、AlLiB(14)、Mg(2)B(14)、MgSi(2)B(12)、MgC(2)B(12)、Li(2)Si(2)B(12)和 Li(2)C(2)B(12)）的结构、力学和电子性质。这些晶体的理论平衡晶格常数与实验值相符。从理论杨氏模量估算的维氏硬度（H(v)）范围为 20-30 GPa，而 MgC(2)B(12)化合物（H(v) = 31.4 GPa）比α-硼硬。根据电子态密度和 Mulliken 布居分析，讨论了硬度的起源以及间隙原子与 B(12)骨架之间的相互作用。B-B 键的键序标度用于解释这些基于 B(12)的三元化合物的硬度。晶体硬度主要由 B(12)二十面体骨架决定，而金属原子的贡献表现为金属到 B 原子的电子转移。我们还计算了 AlMgB(14)和 MgC(2)B(12)的理想拉伸强度，发现它们在拉伸应变下的解理方向分别为<001>和<010>。
