Li Xiao-Feng, Ji Guang-Fu, Zhao Feng, Chen Xiang-Rong, Alfè Dario
School of Physical Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China. Laboratory for Shockwave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, People's Republic of China.
J Phys Condens Matter. 2009 Jan 14;21(2):025505. doi: 10.1088/0953-8984/21/2/025505. Epub 2008 Dec 10.
The structural parameters, elastic constants and electronic structure of NbB(2) under pressure are investigated by using first-principles plane-wave pseudopotential density functional theory within the generalized gradient approximation (GGA). The obtained results are in agreement with the available theoretical data. It is found that the elastic constants and the Debye temperature of NbB(2) increase monotonically and the anisotropies weaken with pressure. The band structure and density of states (DOS) of NbB(2) under pressure are also presented. It is the σ hole that determines the superconductivity in NbB(2), and the features of the σ bands are unchanged after applying pressure except for a shift of position. The density of states (DOS) at the Fermi level decreases with increasing pressure, in conjunction with Bardeen-Cooper-Schrieffer (BCS) theory, which can predict T(c) decreasing with pressure, in agreement with the trend of the theoretical T(c) versus pressure.
采用广义梯度近似（GGA）下的第一性原理平面波赝势密度泛函理论，研究了NbB₂在压力下的结构参数、弹性常数和电子结构。所得结果与现有理论数据一致。研究发现，NbB₂的弹性常数和德拜温度随压力单调增加，各向异性随压力减弱。还给出了NbB₂在压力下的能带结构和态密度（DOS）。是σ空穴决定了NbB₂中的超导性，施加压力后σ带的特征除位置移动外保持不变。费米能级处的态密度（DOS）随压力增加而降低，结合巴丁-库珀-施里弗（BCS）理论，该理论可预测超导转变温度（Tc）随压力降低，这与理论上Tc随压力变化的趋势一致。
