Ground-State Structure and Physical Properties of NB2 Predicted from First Principles

• Published in: 中国物理快报：英文版 2016-03 (3), p.78-81
• Main Author: 吴旌贺 刘长欣
• Format: Article
• Language: English
• Subjects: 基态结构; 密度泛函理论; 机械稳定性; 物理性质; 第一原理计算; 第一性原理; 粒子群优化算法; 结构预测
• ISSN: 0256-307X; 1741-3540
• DOI: 10.1088/0256-307X/33/3/036202

Using the newly developed particle swarm optimization algorithm on crystal structural prediction, we predict a new class of boron nitride with stoicMometry of NB2 at ambient pressure, which belongs to the tetragonal 14m2 space group. Then, its structure, elastic properties, electronic structure, and chemical bonding are investigated by first-principles calculations with the density functional theory. The phonon calculation and elastic constants confirm that the predicted NB2 is dynamically and mechanically stable, respectively. The large bulk modulus, large shear modulus, large Young＇s modulus, and small Poisson＇s ratio show that the 14m2 NB2 should be a new superhard material with a calculated theoretical Vickers hardness value of 66 GPa. Further analysis on density of states and electron localization function demonstrate that the strong B B and 13 N covalent bonds are the main reason for its high hardness in 14m2 NB2.