IrN的结构相变和弹性性质的第一性原理计算

First-principles study on structural phase transition andelastic properties of IrN

采用密度泛函理论的第一性原理赝势平面波方法,结合广义梯度近似(GGA)计算了IrN的结构相变和弹性性质,分别对IrN的岩盐(B1)、氯化铯(B2)、闪锌矿(B3)、纤锌矿(B4)、NiAs(B8)和tungsten carbide(Bh)这6种结构进行了分析,并根据理论计算得到的焓与压强的关系,发现了IrN的相序是B3 → B4 → B8 → B2,相变压强分别发生在1.98 GPa,97.90 GPa和296.64 GPa.通过对B4结构在高压下的弹性特性进行研究,发现其弹性常数、体弹模量、剪切模量、纵波波速、剪切波速以及德拜温度均随压强的增加而单调增大,且依据B/G分析,预测了B4结构能在高压下保持一定的韧性特性.

The present article studied the structural phase transition and elastic properties of IrN by using the pseudopotential plane wave methods within the Perdew-Burke-Ernzerhof (PBE) form of generalized gradient approximation (GGA). Six candidate structures were selected to investigate for IrN, namely, rocksalt (B1), cesium chloride (B2), zinc blende (B3), wurtzite (B4), NiAs (B8) as well as tungsten carbide (Bh) type. On the basis of enthalpy versus pressure data obtained from our theoretical calculations for high-pressure, the article found that the phase sequence of IrN was B3→B4→B8→B2. The obtained phase transitions were at ca. 1.98GPa, 97.90GPa and 296.64 GPa, respectively. Especially, the elastic properties of B4 IrN under high pressure were studied for the first time. The article noted that the elastic constants, the bulk moduli, shear moduli, compressional, shear wave velocities and Debye temperature of B4 IrN increased monotonically with increasing pressure. By analyzing G/B, the brittle-ductile behavior of IrN was assessed.