Goel Satyender, Masunov Artëm E
Nanoscience Technology Center and Department of Chemistry, University of Central Florida, Orlando, Florida 32826, USA.
J Chem Phys. 2008 Dec 7;129(21):214302. doi: 10.1063/1.2996347.
We investigate gas-phase neutral and cationic hydrides formed by 3d transition metals from Sc to Cu with density functional theory (DFT) methods. The performance of two exchange-correlation functionals, Boese-Martin for kinetics (BMK) and Tao-Perdew-Staroverov-Scuseria (TPSS), in predicting bond lengths and energetics, electronic structures, dipole moments, and ionization potentials is evaluated in comparison with available experimental data. To ensure a unique self-consistent field (SCF) solution, we use stability analysis, Fermi smearing, and continuity analysis of the potential energy curves. Broken-symmetry approach was adapted in order to get the qualitatively correct description of the bond dissociation. We found that on average BMK predicted values of dissociation energies and ionization potentials are closer to experiment than those obtained with high level wave function theory methods. This agreement deteriorates quickly when the fraction of the Hartree-Fock exchange in DFT functional is decreased. Natural bond orbital (NBO) population analysis was used to describe the details of chemical bonding in the systems studied. The multireference character in the wave function description of the hydrides is reproduced in broken-symmetry DFT description, as evidenced by NBO analysis. We also propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). The high spin states are build with canonical natural orbitals and do not require SCF convergence.
我们采用密度泛函理论（DFT）方法研究了从钪（Sc）到铜（Cu）的3d过渡金属形成的气相中性和阳离子氢化物。将两种交换关联泛函，即用于动力学的Boese-Martin（BMK）泛函和陶-佩德韦-斯塔罗沃罗夫-斯库塞里亚（TPSS）泛函，在预测键长、能量、电子结构、偶极矩和电离势方面的性能与现有实验数据进行了比较评估。为确保得到唯一的自洽场（SCF）解，我们使用了稳定性分析、费米展宽以及势能曲线的连续性分析。采用了破缺对称性方法以获得对键解离的定性正确描述。我们发现，平均而言，BMK预测的解离能和电离势值比用高水平波函数理论方法得到的值更接近实验值。当DFT泛函中哈特里-福克交换的比例降低时，这种一致性会迅速恶化。使用自然键轨道（NBO）布居分析来描述所研究体系中的化学键细节。如NBO分析所示，在破缺对称性DFT描述中再现了氢化物波函数描述中的多参考特征。我们还提出了一种新方案来校正破缺对称性DFT方法中出现的自旋污染。与传统方案不同，我们的自旋校正针对每个自旋极化电子对单独引入，因此有望产生更准确的能量值。我们推导了一个表达式，用于从低自旋态的破缺对称性DFT描述的能量以及高自旋态（对于两个自旋极化电子对的情况，为五重态和两个自旋污染的三重态）的能量中提取纯单重态的能量。高自旋态由正则自然轨道构建，不需要SCF收敛。
