CoH生成热力学函数的量子力学计算

用B3LYP/SDD密度泛函方法计算了CoH的微观性质、CoH(g)、CoD(g)和CoT(g)的能量(E)和熵(S),进而计算Co与H2、D2、T2反应的△H(-)、△G(-)、△S(-).CoH分子的基电子状态为三重态,Re、D(-)0、ωe分别为1.52nm、277.84 kJ/mol和1321 cm-1,与实验值基本一致.在固态分子的E和S的计算中,以气态分子计算得到的总能量中的振动能Ev代替固态能量,以总熵中的电子振动熵SEv代替固态熵.导出了Co与氢同位素气体反应的△H(-)、△G(-)、△S(-)及平衡氢压力与温度的关系.CoH的室温下平衡离解压力很低,表明CoH是一种稳定的氢化物,这与CoH分子的D(-)0很大的实验事实一致.

Quantmn Mechanical Calculation of the Adsorption of Hydrogen Isotopes on Metallic Cobalt

The thermodynamic functions for the hydrogenating of metal or alloy are very important for hydrogen storage material design. Density functional (B3LYP/SDD) method with Relativistic Effective Core Potential (RECP) have been used to optimize the structure, and to calculate energy E, entropy S and enthalpy H of CoH (D,T). The multiply of the ground state CoH is three, and Re, D 0, ωe are 0.152 nm, 277.84 kJ/mol and 1321 cm-1 respectively, these parameters are agreement with the experimental ones. Considering the characteristics of different motion types, the electronic and vibration energy or entropy of the molecules are assumed to be the corresponding values of their solid states.ΔH , ΔS , ΔG and hydrogen equilibrium pressure of the hydrogenating reaction have been calculated based on this approximation and very obvious isotope effects have been observed. The results show that the present method is reasonable to theoretical study on the thermodynamic functions of hydrogen-storage materials.