A Valence-Bond-Based Multiconfigurational Density Functional Theory: The ?-DFVB Method Revisited.

ABSTRACT: A recently developed valence-bond-based multireference density functional theory, named ?-DFVB, is revisited in this paper. ?-DFVB remedies the double-counting error of electron correlation by decomposing the electron-electron interactions into the wave function term and density functional term with a variable parameter ?. The ? value is defined as a function of the free valence index in our previous scheme, denoted as ?-DFVB(K) in this paper. Here we revisit the ?-DFVB method and present a new scheme based on natural orbital occupation numbers (NOONs) for parameter ?, named ?-DFVB(IS), to simplify the process of ?-DFVB calculation. In ?-DFVB(IS), the parameter ? is defined as a function of NOONs, which are straightforwardly determined from the many-electron wave function of the molecule. Furthermore, ?-DFVB(IS) does not involve further self-consistent field calculation after performing the valence bond self-consistent field (VBSCF) calculation, and thus, the computational effort in ?-DFVB(IS) is approximately the same as the VBSCF method, greatly reduced from ?-DFVB(K). The performance of ?-DFVB(IS) was investigated on a broader range of molecular properties, including equilibrium bond lengths and dissociation energies, atomization energies, atomic excitation energies, and chemical reaction barriers. The computational results show that ?-DFVB(IS) is more robust without losing accuracy and comparable in accuracy to high-level multireference wave function methods, such as CASPT2.

SUBMITTER: Zheng P 

PROVIDER: S-EPMC7863953 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature