State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, P. R. China.
Phys Chem Chem Phys. 2013 Dec 28;15(48):20894-9. doi: 10.1039/c3cp53893a.
Using the first-principles calypso algorithm for crystal structure prediction, we have predicted two orthorhombic Cmcm and Amm2 structures of ZrB4, which are energetically much superior to the previously proposed WB4-, CrB4-, and MoB4-type structures and stable against decompression into a mixture of Zr and B at ambient pressure. The two orthorhombic structures consist of a hexagonal B ring and ZrB12 units connected by edges and one hexagonal B ring in Cmcm and Amm2 structure, respectively. The calculated large shear modulus (e.g., 229 GPa) and high hardness (42.8 GPa for Cmcm and 42.6 GPa for Amm2) reveal that they are potentially superhard materials. The high hardness is attributed to a stacking of B-Zr-B "sandwiches" layers linked by strong covalent B-B bonding.
使用第一性原理 calypso 算法进行晶体结构预测，我们预测了 ZrB4 的两种正交 Cmcm 和 Amm2 结构，它们在能量上远优于先前提出的 WB4-、CrB4-和 MoB4-型结构，并且在环境压力下稳定，不会分解为 Zr 和 B 的混合物。这两种正交结构由六边形 B 环和 ZrB12 单元通过边缘连接而成，在 Cmcm 和 Amm2 结构中分别有一个六边形 B 环。计算出的大剪切模量（例如，229 GPa）和高硬度（Cmcm 为 42.8 GPa，Amm2 为 42.6 GPa）表明它们可能是超硬材料。高硬度归因于由强共价 B-B 键连接的 B-Zr-B“三明治”层的堆叠。
