Abstract We report the structural stability and compressibility behavior of 5B transition metal (TM) monoborides VB and TaB under high pressure. For the study, VB was synthesized in single phase by arc melting method followed by repeated annealing treatments and intermediate grinding; and TaB was procured. High pressure X-ray diffraction studies were carried out using synchrotron X-ray radiation up to 37.5 and 40.5 GPa for VB and TaB, respectively. The ambient orthorhombic lattices were stable for the monoborides in the pressure range studied. The bulk moduli were estimated to be 301(5) and 367(4) GPa, respectively. The axial compressibility was highest along the a direction for both VB and TaB due to predominant presence of metallic TM–TM bonds and absence of covalent B–B bonds along this direction. However, the least compressibility occurred along the c axis for TaB, and along the b axis for VB. The experimental results were substantiated with ab initio electronic structure calculations and the electronic and elastic properties were studied. Both VB and TaB were metallic due to the metallic nature of TM–TM bonds. Study of the density of states (DOS) and charge density distribution revealed that the TM–B bonds exhibited both ionic and covalent nature. The charge transfer from Ta to B was greater than that from V to B. The higher bulk modulus of TaB can be attributed to the stronger B–B covalent bond and enhanced charge transfer between Ta and B. Presence of a pseudogap at Fermi level in both their DOS plots inferred high structural stability. The cause of pseudogap formation was discussed. The study of elastic properties showed that both VB and TaB were mechanically stable in the pressure range studied. Small Pugh and Poisson's ratio indicated that VB and TaB were not ductile or malleable in nature.

中文翻译：

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高压下5B族过渡金属单硼化物的研究

摘要 我们报告了 5B 过渡金属 (TM) 单硼化物 VB 和 TaB 在高压下的结构稳定性和压缩性行为。在研究中，VB 是通过电弧熔化法在单相中合成，然后重复退火处理和中间研磨；并采购了 TaB。对VB 和TaB 分别使用高达37.5 和40.5 GPa 的同步加速器X 射线辐射进行高压X 射线衍射研究。对于所研究的压力范围内的一硼化物，环境正交晶格是稳定的。体积模量估计分别为 301(5) 和 367(4) GPa。由于主要存在金属 TM-TM 键而沿该方向不存在共价 B-B 键，因此 VB 和 TaB 的轴向压缩率最高。然而，TaB 沿 c 轴的可压缩性最小，VB 沿 b 轴的可压缩性最小。实验结果得到了从头算电子结构计算的证实，并研究了电子和弹性特性。由于 TM-TM 键的金属性质，VB 和 TaB 都是金属的。对状态密度 (DOS) 和电荷密度分布的研究表明，TM-B 键表现出离子和共价性质。从 Ta 到 B 的电荷转移大于从 V 到 B 的电荷转移。 TaB 较高的体积模量可归因于更强的 B-B 共价键和增强的 Ta 和 B 之间的电荷转移。他们的 DOS 图都推断出高结构稳定性。讨论了假间隙形成的原因。弹性性能的研究表明，VB 和 TaB 在所研究的压力范围内都是机械稳定的。小的 Pugh 和泊松比表明 VB 和 TaB 本质上没有延展性或延展性。