Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada R3T 2N2.
J Phys Chem A. 2010 Feb 4;114(4):1957-63. doi: 10.1021/jp909576w.
Density functional theory (DFT) calculations using relativistic effective core potentials (RECPs) have emerged as a robust and fast method of calculating the structural parameters and energy changes of the thermochemical reactions of actinide complexes. A comparative investigation of the performance of the Stuttgart small-core and large-core RECPs in DFT calculations has been carried out. The vibrational frequencies and reaction enthalpy changes of several uranium(VI) compounds computed using these RECPs were compared to those obtained using DFT and a four-component one-electron scalar relativistic approximation of the full Dirac equation with large all-electron basis sets (AE). The relativistic AE method is a full solution of the Dirac equation with all spin components separated out. This method gives the "correct" answer (with respect to scalar relativity) which should be closest to experimental values when an adequate density functional is used and in the absence of significant spin-orbit effects. The small-core RECP always show better agreement with the four-component scalar- relativistic AE method than the large-core RECP. We conclude that the 5s, 5p, and 5d orbitals are of great importance in determining the chemistry of actinide complexes. Instances in which large-core RECPs give better agreement with experimental data are attributed to either experimental uncertainties or error cancellations.
密度泛函理论（DFT）计算使用相对论有效核势（RECP）已经成为计算锕系元素配合物的热化学反应的结构参数和能量变化的一种强大而快速的方法。对斯图加特小核和大核 RECP 在 DFT 计算中的性能进行了比较研究。使用这些 RECP 计算的几种六价铀化合物的振动频率和反应焓变与使用 DFT 和全电子四分量单电子标量相对论近似的全 Dirac 方程的计算结果进行了比较，该全电子四分量单电子标量相对论近似使用大的全电子基组（AE）。相对论 AE 方法是带有所有自旋分量的 Dirac 方程的全解。当使用适当的密度泛函且不存在显著的自旋轨道效应时，该方法给出了“正确”答案（相对于标量相对论），这应该最接近实验值。小核 RECP 总是比大核 RECP 更符合四分量标量相对论 AE 方法。我们得出结论，5s、5p 和 5d 轨道对于确定锕系元素配合物的化学性质非常重要。大核 RECP 更符合实验数据的情况归因于实验不确定性或误差抵消。
