Structural stability of intermetallic compound YCu studied by ab initio total energy calculation

High pressure effect on the structural polymorphy of YCu was studied based on the first principle density functional theory. The calculated values of lattice parameters are in good agreement with the available experimental results. The geometry optimization results indicate the anisotropy of the compressibility of FeB-type YCu under high pressure. It is remarkable that the compressibilities along the b- and c-axes experience an abnormality at about 3.3 GPa. Energy calculation results demonstrate that YCu is stable in the FeB-type structure at low temperature and ambient pressure, which is in good agreement with the experimental results. And there exists a structural phase transition from FeB-type structure to CsCl-type structure at the transition pressure of approximate 6.7 GPa. This is the quantitative theoretical prediction of structural phase transition, and it still awaits the experimental confirmation.