铁铬尖晶石结构微变对弹性常数的影响

Influence of the Slight Structural Variation on Elastic Constants of Chromites Spinel

根据第一原理,运用密度泛函(DFT)赝势平面波方法(PWP)和广义梯度近似(GGA),研究了结构微变下的三种铁铬尖晶石晶体模型的晶格结构、弹性及电子特性,并将所得结果与已有的实验值进行了比较.结果表明,晶格常数、体模量和切变模量与得到的实验值符合很好.研究结果显示,结构微变使铁铬尖晶石的体模量减小;随着氧原子位置u增大,杨氏模量明显增大,切变模量和泊松比显著减小.通过对微变结构的铁铬尖晶石电子特性诸如态密度,最近邻铁、铬阳离子与氧离子键长及集居数的分析发现,Fe,Cr两种阳离子间电子交换作用是影响铁铬尖晶石结构弹性性质变化的主要因素.

According to the first principles, the lattice structure, elasticity and electronic properties of three kinds of chromites spinel subject to slight structural variation are studied by the pseudowaves plane （PWP） approach based on density functional theory （DFT） and generalized gradient approximation （GGA）. The calculated and experimental results are compared and show that the values of lattice constant, bulk module and shear module are all in good agreement. The slight structural variation enables the bulk modulus to decrease considerably and the Young＇s modulus increases clearly with increasing coordinate value of atomic oxygen, but the shear modulus and Poisson ratio decreases substantially. It is concluded that the electron exchange action between iron and chromium actions is the main influencing factor on the variation of the elasticity after analyzing the electronic properties such as DOS （density of states）, the most nearest-neighboring bond lengths between Fe/Cr actions and O anion and electronic populations.