镍基超导母体材料EuNi_2Si_2的结构和热力学性质研究

Structure and thermodynamic properties of Ni based superconductive material EuNi_2Si_2

应用Chen-Mbius晶格反演获得的原子间相互作用势,对镍基超导母体材料EuNi2Si2不同空间群的结构进行结构弛豫、切变拉伸、随机扰动和X射线衍射谱的分析.研究表明,空间群号为139结构的EuNi2Si2母体材料能量最低,结构最稳定.另外,还计算了空间群号为139稳定晶格结构的声子态密度和热力学性质.计算结果表明:对于声子态密度,原子质量较大的稀土元素Eu在低频范围内贡献最大,随着频率的升高,原子质量较小的元素Si的贡献越来越突出;对于比热容和振动熵,在低温区元素Eu和Ni的贡献较大,随着温度的升高,元素Si的贡献越来越突出.

We investigate the structure stability,stretching,compressing,shearing,random shifting and X-ray diffraction of Ni based superconductive material EuNi2Si2 with different space group numbers based on inversed interatomic potentials obtained with Chen-Mbius lattice-inversion technique.It is found that the space group number of 139 has the lowest binding energy and the structure is the most stable.Furthermore,the phonon density and the thermodynamic properties of the stable structure are calculated and discussed.The phonon density of states shows that the low frequency range is dominated by the rare-earth element Eu with larger atomic mass.While with frequency increasing,the Si atoms with smaller atomic mass become more and more prominent.For the specific heat and the vibrational entropy,Eu and Ni contribute more in the low temperature range,Si becomes more and more prominent with temperature increasing.