Pu(100)表面吸附CO_2的密度泛函研究

Density functional study of CO_2 adsorption on Pu(100) surface

采用广义梯度密度泛函理论的改进Perdew-Burke-Ernzerh方法结合周期性层晶模型,研究了CO2分子在Pu(100)面上的吸附和解离.吸附能和几何构型的计算表明,CO2以穴位C4O4构型吸附最为有利,吸附能为1.48eV.布居分析和态密度分析表明,CO2与Pu表面相互作用的本质主要是CO2分子的杂化轨道2πμ与Pu5f,Pu6d,Pu7s轨道通过强电子转移和弱重叠杂化的方式相互作用而生成了新的化学键.计算的CO2→CO+O解离能垒为0.66eV,解离吸附能为2.65eV,表明在一定热激活条件下CO2分子倾向于发生解离性吸附.O2,H2,CO和CO2在Pu(100)面吸附的比较分析表明,较低温度下的吸附强度顺序依次为O2,CO,CO2,H2;较高温度下的吸附强度顺序依次为O2,CO2,CO,H2.

The adsorption of CO2 on Pu（100） surface has been studied with periodic slab model by revised Perdew-Burke-Ernzerh approximation within the framework of density functional theory. The optimized results of adsorption energies and geometrical structures show that the H-C4O4-type adsorption is optimum adsorption mode with adsorption energy of 1.48 eV. The atomic population and density of states analysis indicate that the interaction between Pu atom and CO2 molecule results mainly from strong electron transfer and weak overlap-hybridization between molecular orbital 2πμ of CO2 molecule and Pu5f,Pu6d and Pu7s orbitals of surface Pu atom. The calculated activation barrier and adsorption energy CO2→CO＋O dissociative reaction are 0.66 and 2.65 eV,respectively,which indicates the dissociative adsorption of CO2 on Pu（100） surface is favorable under the certain heat activation condition. The comparison of O2,H2,CO and CO2 adsorption on Pu（100） surface indicates the adsorption strength follows the ordering：O2,CO,CO2,H2 and O2,CO2,CO,H2 at lower and higher temperature,respectively.