Fast and Accurate Computation of Nonadiabatic Coupling Matrix Elements Using the Truncated Leibniz Formula and Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory

• DOI: 10.1021/acs.jpclett.1c00932
• Publication Date: 2021-05-13T12:34:19Z
• Authors: Seunghoon Lee; Yevhen Horbatenko; Michael Filatov; Cheol Ho Choi
• Keywords: Density matrix; Coupled cluster; Matrix (chemical analysis)

We present a fast and accurate numerical algorithm for computing the first-order nonadiabatic coupling matrix element (NACME). The employs truncated Leibniz formula (TLF) approximation within finite-difference method, which makes it easily applicable in connection with any wave function-based methodology. In this work, we used recently developed mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT, MRSF brevity). accuracy is assessed NACME between singlet electronic states of dissociating hydrogen molecule. It demonstrated that an intermediate approximation, TLF(1), affords negligible numeric error on order ∼10–10 a.u. while enabling computation NACME. As method yields correct description dissociation curves H2 all involved, TLF(1)/MRSF values are excellent agreement reference analytical obtained by full configuration interaction. For polyatomic molecules, NAC vectors agree very closely MRCISD vectors. Hence, proposed protocol promising tool evaluation NACMEs.