Due to high melting point,high strength,strong oxidation resistance and deformation resistance at el-evated temperature,refractory metal silicides have attracted extensively attention.In the refractory metal sili-cides,the tungsten-silicon binary compounds,where tungsten has the highest melting point,not only have the similar mechanical and physical properties compared to other metal silicides,but also show many other excellent performance characteristics.The theoretical investigation of tungsten-silicon binary compounds was presented by first-principles calculation to fully exploit the potential performance of tungsten-silicon binary compounds. Two prototype structures of WSi2compounds and three prototype structures of W5Si3compounds had been taken into account:α-WSi2(C40),β-WSi2(C11b),W5Si3-prototype structure (D8m),Cr5B3-prototype structure (D8l)and Mn5Si3-prototype structure (D88).The formation enthalpies were calculated to analyze the stabili-ties,and the elastic constants,bulk modulus,shear modulus,tensile modulus,Poisson's ratio,anisotropy fac-tor and Vickers hardness were calculated to obtain the mechanical properties.Otherwise,the total and partial density of states were also calculated to obtain the bonding mechanisms of tungsten-silicon binary compounds. The stability calculation indicated that the stability sequence of the five tungsten-silicon compounds forms the following order:β-WSi2>α-WSi2>W5Si3-prototype structure>Mn5Si3-prototype structure>Cr5B3-prototype structure,and the results of density of state further verified it.The calculation results of mechanical properties showed that the five stable phases of WSi2and W5S3with good shape,toughness and hardness are agreement with the mechanical stability.Among them,the shape,toughness and hardness ofβ-WSi2are the highest,while those of Cr5B3-prototype structure are the lowest.The calculation of elastic constants showed that for α-WSi2, Mn5Si3-prototype structure,W5Si3-prototype structure and Cr5B3-prototype structure,the bondings along [100]and[010]directions are stronger than that along [001]direction,and the[100](010)shear is easier than [100](001)shear.On the contrary,forβ-WSi2,the bondings along [100]and [010]directions are weaker than that along [001]direction,and the [100](010)shear is similar with the [100](001)shear.The results of total and partial density of states exhibited that the bonding mechanisms of these five compounds are all the mixture of strong covalent and certain metal bonds.In this paper,a new idea and theoretical foundation of new materials based on tungsten-silicon binary compounds will be provided.%钨硅二元体系化合物除了具有难熔金属硅化物共有的高熔点、高强度、强的抗氧化性和抗形变能力的同时,还表现出了许多其它卓越的性能特点,目前已得到广泛的应用.基于密度泛函理论对钨硅二元体系所形成化合物WSi2和W5Si3的稳定性、力学性能和电子结构进行了研究.通过计算5种钨硅二元体系相结构的点阵常数、形成焓、弹性常数、体模量、剪切模量、拉伸模量、泊松比、各向异性因子以及维氏硬度等物理量得到其晶体结构和力学性能等信息.此外,通过对WSi2和W5Si3的总体和局部态密度的计算得到钨硅二元体系化合物的成键机制.计算结果表明,在钨硅二元体系化合物的5种稳定相结构中,β-WSi2表现出了最高的稳定性和力学性能.态密度的计算结果也进一步证实了这一点.同时,态密度的计算结果表明这5种稳定相结构的成键机制均是较强的共价键和一定程度金属键的混合.结果可对基于钨硅二元体系化合物的新材料的设计提供新线索和理论基础.
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