Institute for Computational Materials Science, School of Physics and Electronics, Henan University, Kaifeng 475004, PR China.
Chemphyschem. 2013 Apr 15;14(6):1245-55. doi: 10.1002/cphc.201201009. Epub 2013 Feb 25.
Phase stability is important to the application of materials. By first-principles calculations, we establish the phase stability of chromium borides with various stoichiometries. Moreover, the phases of CrB3 and CrB4 have been predicted by using a newly developed particle swarm optimization (PSO) algorithm. Formation enthalpy-pressure diagrams reveal that the MoB-type structure is more energetically favorable than the TiI-type structure for CrB. For CrB2, the WB2-type structure is preferred at zero pressure. The predicted new phase of CrB3 belongs to the hexagonal P-6m2 space group and it transforms into an orthorhombic phase as the pressure exceeds 93 GPa. The predicted CrB4 (space group: Pnnm) phase is more energetically favorable than the previously proposed Immm structure. The mechanical and thermodynamic stabilities of predicted CrB3 and CrB4 are verified by the calculated elastic constants and formation enthalpies. The full phonon dispersion calculations confirm the dynamic stability of WB2 -type CrB2 and predicted CrB3. The large shear moduli, large Young's moduli, low Poisson ratios, and low bulk and shear modulus ratios of CrB4-PSC and CrB4-PSD indicate that they are potential hard materials. Analyses of Debye temperature, electronic localization function, and electronic structure provide further understanding of the chemical and physical properties of these borides.
相稳定性对于材料的应用很重要。通过第一性原理计算，我们建立了具有不同化学计量比的铬硼化物的相稳定性。此外，我们还使用新开发的粒子群优化（PSO）算法预测了 CrB3 和 CrB4 的相。形成焓-压图表明，对于 CrB，MoB 型结构比 TiI 型结构更具能量优势。对于 CrB2，在零压下，WB2 型结构更占优势。预测的 CrB3 新相属于六方 P-6m2 空间群，当压力超过 93 GPa 时，它会转变为正交相。预测的 CrB4（空间群：Pnnm）相比以前提出的 Immm 结构更具能量优势。通过计算弹性常数和形成焓验证了预测的 CrB3 和 CrB4 的力学和热力学稳定性。全声子色散计算证实了 WB2 型 CrB2 和预测的 CrB3 的动力学稳定性。CrB4-PSC 和 CrB4-PSD 的大剪切模量、大杨氏模量、低泊松比以及低体弹模量比和切变模量比表明它们是潜在的硬质材料。德拜温度、电子局域函数和电子结构的分析为这些硼化物的化学和物理性质提供了进一步的理解。
