PdH、YH体系的结构与氢化反应的平衡压力

用相对论有效原子实势(RECP/SDD)和密度泛函(B3LYP)方法对PdH、YH体系的结构进行了优化,同时用Murrell-Sorbie函数导出PdH、YH分子的势能函数和光谱常数;得到PdH分子的基态为X2∑+,RPdH=0.154 1 nm,离解能De=2.511 eV,谐振频率ωe=2 019.458 9 cm-1;YH分子的基态为X1∑+,RYH=0.191 9 nm,离解能De=4.308 eV,谐振频率ωe=1 497.531 2 cm-1;并得到一键长为0.200 3nm,De=3.488 eV,ωe=1 309.318 2 cm-1的YH分子激发态.并根据以分子总能量中的振动能Ev代替固态能量,以电子和振动熵SEv代替固态熵的近似方法,计算了不同温度下Pd、Y与H2、D2、T2反应的一氢化物热力学函数△Hθ、△Gθ、△Sθ及氢化反应平衡压力,导出了与温度的依赖关系,结果表明:PdH(S)的生成焓为32.05kJ·md-1,与实验值37.30kJ·mol-1接近,YH(S)的生成焓为70.21 kJ·mol-1.

The structure and equilibrium pressure for the Pd- H, Y- H system

Density functional (B3L YP) method with relativistic effective core potential (RECP) has been used to optimize the structures of PDH and YH molecules. The spectral constants and the potential energy function are derived from the function of Murrell-Sorbie. The results show that the bond lengths of PDH (X2∑+ and YH(X1∑+) molecules are RpdH=0.154 1 nm and RyH=0.191 9nm, and the harmonic frequencies we are 2019.4589cm-1,and the dissociation energies Deare 2.511 eV and 4.309 eV, respectively. At the same time, a excited state of YH, RyH=0.200 3 nm and we=1 309.318 2cm-1 and De=3.488 eV, has also been obtained. The electronic and vibrational energy or entropy of the molecules is assumed to be the corresponding values of their solid states, and the △Hθ、△Gθ、△Sθ and hydrogen equilibrium pressure of different temperatures are obtained by this approximation. The results show that the PdH(s) jeat of formation is 32.05 kJ.mol-1, which is near the value of experiment 37.3kJ.mol-1, and the YH heat of fomation is 70.21 kJ.mol-1.