钇元素的高压结构及其性质

High Pressure Structures and Properties of Element Yttrium

基于第一性原理密度泛函理论方法和晶体结构预测(CALYPSO)等研究手段,对钇物质的高压晶体结构及性质进行了理论研究。用CALYPSO预测出钇的两个新高压相:Fddd和Fmm2结构,确定了钇的高压结构相变序列并给出了具体的相变压力,钇dfcc在109GPa时相变到Fddd结构,在524GPa时Fddd相变到Fmm2结构。Fddd和Fmm2结构均为正交晶系,其中Fddd结构每个晶胞中含有4个原子,Fmm2结构每个晶胞中含有12个原子。为了研究这两个高压相的电子性质及力学性质,计算了它们的电子局域函数、弹性常数以及力学参数,结果指出这两个高压新相均满足力学稳定性判据。

High pressure structural phase transitions of element yttrium are studied by using the unbiased Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) structure prediction method combined with first-principles calculations and density functional theory (DFT). Two previously unknown phases of yttrium with space group Fddd and Fmm 2 symmetry under ultrahigh pressure have been discovered. The phase transition sequence of yttrium high-pressure structure is determined and the specific phase transition pressure is given. The yttrium dfcc phase transition to Fddd structure takes place at 109 GPa and then phase transition to Fmm 2 structure at 524 GPa. The Fddd and Fmm 2 structures are all orthorhombic crystals, in which Fddd structure contains 4 atoms, and Fmm 2 structure contains 12 atoms in each crystal cell. In order to study the electronic properties and mechanical properties of the two high pressure phases, we subsequently calculate ELF, elastic constants and mechanical parameters of the Fddd and Fmm 2 structures. The results show that the two phases are mechanically stable.