二氮化铂高压结构相变，弹性和热力学性质的第一性原理计算

Phase transition, elastic and thermodynamic properties of PtN2 under high pressure from first-principles study

摘要:

运用密度泛函理论广义梯度近似方法计算了PtN2在莹石结构（C1），黄铁矿结构（C2），白铁矿结构（C18），CoSb2结构，简单六角结构（SH），简单四角结构（ST）和层状结构（LS）的结构参数，弹性性质，电子结构和热力学性质。计算了平衡态晶格参数，体模量 和它的一阶导数。计算得到人焓表明，最稳定的结构为C2结构，其他的为亚稳态结构。而在我们研究的压强范围内没有发生相变。C2结构的态密度表明它是一种具有1.5eV带隙的半导体。另外，我们还预测了杨氏模量，泊松比和各向异性因子。弹性常数，体模量，切变模量，横向声速和剪切声速随着压强的增大而单调增大。德拜温度，热膨胀系数和热容随压强增大而增大。

Abstract:

The structural, elastic, electronic and thermodynamic properties of PtN2 have been studied in fluorite (C1), pyrite (C2), marcasite (C18), CoSb2, simple hexagonal (denoted SH hereafter), simple tetragonal (denoted ST hereafter) and Layer structure (hereafter denoted as LS) phase by performing ab initio calculations within the generalized gradient approximation (GGA). The equilibrium lattice parameters, bulk modulus and its pressure derivative are in agreement with the available theoretical results and experimental data. The most stable structure is C2 phase through calculating the enthalpy, while the others are metastable. It is noted that no phase transition occurs between difference phases in the pressure range studied here. The density of states indicates that C2-PtN2 is semiconductor with a band gap of 1.5 eV. The Young's modulus, Poisson's ratio and anisotropy factor have been predicted. We note that the elastic constant, bulk modulus, shear modulus, compressional and shear wave velocity increase monotonically with increasing pressure. The Debye temperature, thermal expansion and heat capacity increase with pressure.