arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1009.0458cond-mat.mtrl-sci
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铂金属氮化物的热力学基态

Thermodynamic ground states of platinum metal nitrides

Daniel Åberg, Babak Sadigh, Jonathan Crowhurst, Alexander F. Goncharov

摘要:

用密度泛函理论系统地研究了铂族氮化物各相的热力学稳定性。结果表明,对于Rh,Pd,Ir和Pt的氮化物,两种新的晶体结构,其中金属离子占据简单的四方晶格位置,在环境条件下具有较低的形成比任何先前提出的结构。相对于这些结构的稳定区域扩展到17 GPa的PtN2。计算表明,在此压力下的PtN2简单的四元结构是热力学稳定的相分离。进一步讨论了局部密度和广义梯度近似预测的绝对形成常数的不同值以及简单四斜晶系与黄铁矿或白铁矿结构之间的不同相对稳定性的事实。

英文摘要:

The thermodynamic stabilities of various phases of the nitrides of the platinum metal elements are systematically studied using density functional theory. It is shown that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability with respect to those structures extends to 17 GPa for PtN2. Calculations show that the PtN2 simple tetragonal structures at this pressure are thermodynamically stable also with respect to phase separation. The fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures are further discussed.

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