Explicit construction of diabatic state and its application to the direct evaluation of electronic coupling

Abstract

A valence bond (VB) block-diagonalization approach, named VBBDA, is proposed to construct the charge-localized diabatic state explicitly within the framework of ab initio VB theory. Since the VB structure built upon the localized orbitals represents the charge localized character of the diabatic state faithfully, we are able to obtain accurate electronic coupling between diabatic states by using a very compact VB wave function. Moreover, the potential energy curves of the diabatic states and hence the crossing points of them can be accurately evaluated. The pilot applications showed that the electronic couplings computed by the VB method are consistent with the complete active space self-consistent field method and may even be close to the results of other high-level ab initio methods such as full configuration interaction and multireference configuration interaction. In addition, the computed electronic couplings show the expected exponential attenuation for the donor-acceptor systems as the distance increases. Moreover, VBBDA has the capability for handling complicated systems based on either two-state or multi-state treatment. Finally, because of the outstanding performance of the Xiamen Valence Bond software package, which is an ab initio VB program, VBBDA is capable for systems consisting more than 1000 basis functions.

Diabatization around Conical Intersections with a New Phase-Corrected Valence-Bond-Based Compression Approach

“…In addition, if a global diabatic representation were known, we could circumvent the heavy task of calculating such couplings around conical intersections; unfortunately, such a representation is not available directly and must be constructed with some diabatization scheme, which relies on the choice of a diabatic criterion. Among them, ab initio diabatization approaches are based on the properties of adiabatic electronic wave functions in terms of configurations [1][2][3][4][5][6][7][8][9][10][11][12][13] . Recently, a valence-bond-based compression approach for diabatization (VBCAD) has been proposed 14 ; it allows a low-size diabatic Hamiltonian matrix to be built automatically.…”

“…In addition, if a global diabatic representation were known, we could circumvent the heavy task of calculating such couplings around conical intersections; unfortunately, such a representation is not available directly and must be constructed with some diabatization scheme, which relies on the choice of a diabatic criterion. Among them, ab initio diabatization approaches are based on the properties of adiabatic electronic wave functions in terms of configurations. − Recently, a valence-bond-based compression approach for diabatization (VBCAD) has been proposed; it allows a low-size diabatic Hamiltonian matrix to be built automatically. The central idea is to reduce, i.e., compress, the full electronic Hamiltonian matrix upon employing a series of Householder transformations coupled to a VB-based diabatization criterion, which take explicit advantage of Lewis VB structures with specific bonding patterns.…”

Electronic Couplings for Photoinduced Charge Transfer and Excitation Energy Transfer Based on Fragment Particle–Hole Densities

“…The accurate and efficient calculation of electronic couplings for complex molecular systems has been a long-standing issue, which usually requires one to construct well-defined quasi-diabatic states. Methods like the constrained density functional theory, , the valence bond theory, − and the multistate density functional theory − directly construct quasi-diabatic states either by imposing constraints on the electron densities or by using chemically intuitive localized configurations. On the other hand, it is well-known that conventional electronic structure calculations under the Born–Oppenheimer approximation only offer adiabatic state properties.…”

A Novel Valence-Bond-Based Automatic Diabatization Method by Compression

“…Therefore, classical VB theory appears as a natural choice from a chemical perspective in the construction of diabatic states. Recently, ab initio classical VB methods and block-localized wave function (BLW), which is a type of semilocalized VB method that uses a single-determinantal wave function built on semilocalized molecular orbitals, have been successfully employed in the direct construction of diabatic states, based on the assumption that an educated inspection of dominant VB structure sets can be associated with the diabatic states. − …”