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Density functional theory study of the relative stability of the iron disulfide polymorphs pyrite and marcasite

机译:二硫化铁多晶型黄铁矿和镁铁矿相对稳定性的密度泛函理论研究

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The performance of density functional theory has been widely examined with regard to its ability to predict the properties of minerals, though less attention has been given to the correct determination of the relative stability of structurally similar polymorphs. Here a detailed examination is performed of the numerical and theoretical factors that may influence the structure and relative energetics of two such polymorphs of iron disulfide, namely, pyrite and marcasite, within density functional theory. Both the local-density approximation and commonly used generalized gradient approximation exchange-correlation functionals, such as Perdew, Burke and Ernzerhof (PBE), are found to predict that marcasite is more stable than pyrite, at variance with experiment. Allowing for the zero-point energy of vibration fails to remedy this discrepancy. While inclusion of a sufficiently large Hubbard U parameter for iron is found to reverse the stability, this comes at the expense of a very poor description of other properties. Examination of three generalized gradient approximations developed specifically for the solid state, namely, AM05, Wu-Cohen and PBEsol, demonstrates that all of these functionals offer a superior description of the structures and relative energies of pyrite and marcasite through correctly predicting that the former is the ground-state phase at ambient conditions.
机译:尽管密度泛函理论预测矿物特性的能力得到了广泛的研究,但是对结构相似多晶型物相对稳定性的正确测定却很少关注。这里,在密度泛函理论范围内,对可能影响二硫化铁的两种这样的多晶型物黄铁矿和镁铁矿的结构和相对能量的数值和理论因素进行了详细的研究。发现局部密度近似和常用的广义梯度近似交换相关函数(例如Perdew,Burke和Ernzerhof(PBE))都可以预测,与实验不同,镁铁矿比黄铁矿更稳定。允许零点振动能量无法弥补这一差异。虽然发现为铁包含足够大的Hubbard U参数会颠倒稳定性,但这是以对其他性能的描述很差为代价的。对专门为固态而开发的三个广义梯度梯度近似进行检验,即AM05,Wu-Cohen和PBEsol,表明所有这些官能团通过正确预测前者为黄铁矿和镁铁矿,提供了对黄铁矿和镁铁矿的结构和相对能的出色描述。在环境条件下的基态相位。

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