中文摘要：

采用基于密度泛函理论第一性原理和相干势近似计算，研究MnFeP1-xSix（0.33〈x〈0.66）化合物的力学性质随Si掺杂组分以及占位有序性的变化规律，讨论了多晶材料的韧脆性等力学性能与Si掺杂浓度的关联．研究结果表明：Si的占位有序性并不显著影响MnFeP1-xSix（0.33〈x〈0.66）化合物的结构参数和磁性；随着Si组分的增加材料的体模量增加，并且显著地依赖Si在1b和2c晶位的有序占位；多晶材料的韧脆性基本与Si组分无关，在所考虑的Si组分范围内化合物均呈脆性，说明MnFeP1-xSix（0.33〈x〈0.66）化合物脆性并非来自Si替代P，因此可考虑用过渡金属掺杂提高其韧性．

英文摘要：

The Si concentration and site occupation order dependence of the mechanical properties of hexagonal MnFeP1-xSix compounds are studied by Density Functional Theory in combination with the coherent potential approximation. It is found that the occupation order of Si on two different sublattices do not obviously affect the structural and magnetic properties of MnFeP1-xSix compounds. Further investigation on Si concentration dependence of the mechanical properties of polycrystalline MnFeP1-xSix compounds show that the bulk moduli of the compounds decrease for the increasing Si concentration. And Bulk moduli significantly depend on the atomic order of the Si at lb and 2c sites. The MnFeP1-xSix compounds are always brittle in the considered concentration range of Si, demonstrating that the brittleness is not originated from the Si substitution of P. For further study, transition metal doping could be a possible route for increase ductility of the compounds.