Batista Enrique R, Martin Richard L, Hay P Jeffrey, Peralta Juan E, Scuseria Gustavo E
Los Alamos National Laboratory, Theoretical Division, MS B268, New Mexico 87545, USA.
J Chem Phys. 2004 Aug 1;121(5):2144-50. doi: 10.1063/1.1768518.
The structural properties and thermochemistry of UF6 and UF5 have been investigated using both Hartree-Fock and density functional theory (DFT) approximations. Within the latter approach, the local spin-density approximation, the generalized gradient approximation, and hybrid density functionals were considered. To describe the uranium atom we employed small-core (60 electrons) and large-core (78 electrons) relativistic effective core potentials (RECPs), as well as the all-electron approximation based on the two-component third-order Douglas-Kroll-Hess Hamiltonian. For structural properties, we obtained very good agreement with experiment with DFT and both large and small-core RECPs. The best match with experiment is given by the hybrid functionals with the small-core RECP. The bond dissociation energy (BDE) was obtained from the relative energies of the fragments [UF6 --> UF5 + F], corrected for zero-point energy and spin-orbit interaction. Very good agreement was found between the BDE obtained from all-electron calculations and those calculated with the small-core RECP, while those from the large-core RECP are off by more than 50%. In order to obtain good agreement with experiment in the BDE it is imperative to work with hybrid density functionals and a small-core RECP.
利用哈特里-福克方法和密度泛函理论（DFT）近似对六氟化铀（UF6）和五氟化铀（UF5）的结构性质和热化学性质进行了研究。在后者的方法中，考虑了局域自旋密度近似、广义梯度近似和杂化密度泛函。为了描述铀原子，我们采用了小核（60个电子）和大核（78个电子）相对论有效核势（RECP），以及基于双组分三阶道格拉斯-克罗尔-赫斯哈密顿量的全电子近似。对于结构性质，我们通过DFT以及大核和小核RECP与实验结果取得了很好的一致性。与实验的最佳匹配由采用小核RECP的杂化泛函给出。键解离能（BDE）从碎片[UF6→UF5 + F]的相对能量获得，并对零点能和自旋轨道相互作用进行了校正。全电子计算得到的BDE与小核RECP计算得到的BDE之间发现了很好的一致性，而大核RECP得到的BDE偏差超过50%。为了在BDE方面与实验取得良好的一致性，必须使用杂化密度泛函和小核RECP。
