PdY合金及其一氢化物分子结构及热力学函数的研究

本文利用B3LYP的密度泛函方法对PdY、 PdYH的分子结构进行了优化,得到PdY最稳定的电子态为2∑,RPdY=0.2418 nm,ωe=249.66cm-1,De=2.75eV.PdYH最稳定构型为Cs,1A'态,RPdY=0.243 0 nm,RYH=0.197 4nm,∠PdYH=116.54°,谐振频率v1(a')=1 450.83cm-1,v2(a')=351.21cm-1,v3(a')=243.71cm-1,离解能De(PdYH)为5.64 eV.并以气态分子总能量中的振动能Ev代替分子处于固态时的振动能,以电子运动和振动运动熵SEv代替分子处于固态的熵的近似方法计算了PdY与氢及其同位素反应的△Hθ、△Sθ、△Gθ及氢化反应平衡压力,得出PdYH(S)的生成焓为60.32kJ·mol-1.

The study for the structures of PdY, PdYH and the thermodynamic function of PdYH(D,T)

The structures of PdY and PdYH have been optimized by density functional theory (B3LYP) and Relativistic Effective Core Potential (RECP) method. The results show that the ground states for PdY and PdYH are of ()~2Σ and ()~1A′ symmetry respectively. For PdY molecule, the bond length (R_(PdY)) is 0.241 8 nm, and the harmonic frequency (ω_e) and the dissociation energy (D_e) are 249.66 cm~(-1) and 2.75?eV respectively. For PdYH molecule, the structure parameters R_(PdY), R_(YH) and ∠PdYH are 0.243 0 nm, (0.197 4) nm and 116.54° respectively, and the dissociation energy (D_e(PdYH)) is 5.64 eV and the vibrational frequencies are 1 450.83 cm~(-1), 351.21?cm~(-1) and 243.71 cm~(-1). Furthermore, to calculate enthalpy H and entropy S of solid PdYH, PdYD and PdYT, the vibrational energy or electronic and vibration entropy of the molecules are assumed to be the corresponding values of their solid states. The thermodynamic function ΔH~θ,ΔS~θ,ΔG~θ of PdYH、PdYD and PdYT have also been calculated by this approximation method,and based on this results,the present have obtained hydrogen isotope equilibrium pressure of the hydrogenating reaction.The enthalpy of formation of PdYH(s) is 60.32kj.mol-1 at 298.15k.