铀的原子模型

Atomistic Model of Uranium

在U价电子采用（5s4p3d4f）／[3s3p2d2f]收缩基函数，原予实采用相对论原子实势进行处理的条件下，通过B3LYP杂化交换一相关泛函对U2分子的电子态和势能数据进行了第一性原理计算．结果表明u2分子的基态电子态为X^9∑g^＋．同时用Murrell—Sorbie解析势能函数对对势数据进行拟合．在自旋极化水平和广义梯度近似下，采用密度泛函理论（DFT）和Perdew-Burke-Ernzerho跤换一相关泛函确定了U．U嵌入原子方法（EAM）的作用势，其中采用物理性质（比如内聚能、晶格常数、体积模量、剪切模量、简单立方（sc）和面心立方（fcc）的相对能、六角密排（hcp）和面心立方（fcc）的相对能以及单空位形成能）来计算EAM势能参数．第一性原理方法确定的u—U对势与EAM势能参数定义的对势一致．在fcc结构中，采用EAM势能参数获得的单空位形成能同样与DFT计算结果一致．

The electronic state and potential data of U2 molecules are performed by first principle calculations with B3LYP hybrid exchange-correlation functional, the valence electrons of U atom are treated with the （5s4p3d4f）/[3s3p2d2f] contraction basis sets, and the cores are approximated with the relativistic effective core potential. The results show that the ground electronic state is x^9∑g＋. The pair potential data are fitted with a Murrell-Sorbie analytical potential function. The U-U embedded atom method （EAM） interatomic potential is determined based on the generalized gradient approximation calculation within the framework of the density functional theory using Perdew-Burke-Ernzerhof exchange-correlation functional at the spin-polarized level. The physical properties, such as the cohesive energy, the lattice constant, the bulk modulus, the shear modulus, the sc/fec relative energy, the hep/fce rela- tive energy, the shear modulus and the monovacaney formation energy are used to evaluate the EAM potential parameters. The U-U pair potential determined by the first principle calculations is in agreement with that defined by the EAM potential parameters. The EAM calculated formation energy of the monovacancy in the fee structure is also found to be in close agreement with DFT calculation.