Birke Ronald L
Department of Chemistry, The City College of New York, and The Graduate School and University Center of the City University of New York, New York, New York 10031, USA.
J Chem Phys. 2024 May 7;160(17). doi: 10.1063/5.0175182.
The ground state of 3d1 MnO42- was studied by density functional theory (DFT) and complete active space self-consistent field (CASSCF) methods in terms of a variety of molecular point group structures to ascertain the site and Jahn-Teller (JT) distortion effect. Modeling results from UB3LYP/6-31+G(d) calculations with natural bond orbital analysis show the four Mn-O bonds are coordinate covalent. The one-electron matrix elements from CASSCF(AILFT) (ab initio ligand field theory) with a second order perturbation treatment were used to calculate the parameters of the angular overlap model. These allowed the calculation of JT stabilization energies and first and second order JT coupling constants for MnO42- with C2v and D2d symmetry. Absorption spectra and excited state transition energies were calculated assuming the lattice distorted geometry was C2v with time-dependent DFT (TDDFT) using the unrestricted coulomb-attenuating UCAM-B3LYP density functional and with the spin-adapted spin-flip DFT using the UBH&HLYP density functional, both with the AUG-CC-PVTZ basis set. The mean absolute deviation of the calculations from experimental excited states for the ligand field and ligand-to-metal charge transfer (LMCT) bands was better than 0.1 eV. Several new assignments for LMCT excited states were made on the basis of the TDDFT excitation results.
采用密度泛函理论（DFT）和完全活性空间自洽场（CASSCF）方法，在多种分子点群结构下研究了3d1 MnO42-的基态，以确定位点和 Jahn-Teller（JT）畸变效应。基于自然键轨道分析的UB3LYP/6-31+G(d)计算结果表明，四个Mn-O键为配位共价键。利用CASSCF（从头算配体场理论）的单电子矩阵元并进行二阶微扰处理，计算了角重叠模型的参数。由此计算了具有C2v和D2d对称性的MnO42-的JT稳定能以及一阶和二阶JT耦合常数。使用无限制库仑衰减UCAM-B3LYP密度泛函和使用UBH&HLYP密度泛函的自旋适应自旋翻转DFT，并结合AUG-CC-PVTZ基组，通过含时密度泛函理论（TDDFT），在假设晶格畸变几何为C2v的情况下计算了吸收光谱和激发态跃迁能量。对于配体场和配体到金属电荷转移（LMCT）带，计算结果与实验激发态的平均绝对偏差优于0.1 eV。基于TDDFT激发结果，对LMCT激发态进行了若干新的归属。
