Fast quantum chemistry calculations for large molecules and condensed-phase systems: The developments and applications of generalized energy-based fragmentation approach

Abstract

The GEBF approach could be applied to the ground-state energies (including the relative energies or binding energies) of a broad range of large systems including molecular clusters, supramolecular systems, proteins, nucleic acids, and etc. The computational levels include HF, DFT, second-order Moller-Plesset perturbation theory (MP2), coupled cluster singles and doubles (CCSD), CCSD with triples correction [CCSD(T)], and explicitly correlated MP2-F12 and CCSD(T)-F12 x ( x = a , b ) methods. With the GEBF energy derivatives (including energy gradients, Hessians, and so on), the approaches could be employed for optimizing the molecular geometries, performing ab initio molecular dynamics, computing the vibrational spectroscopies (including the IR and Raman spectroscopies) and nuclear magnetic resonance (NMR) chemical shifts of large systems at the HF, DFT, and MP2 levels. GEBF approach is also extended to the localized excited states by defining those subsystems including local excitation as the active subsystems, which are treated by the excited-state calculations at the time-dependent DFT or approximate equation-of-motion CCSD (CC2) levels. Then the GEBF-TDDFT or GEBF-CC2 could be used to compute electronic absorption spectra of solutions or large molecules with local excitations. The GEBF approach under the periodic boundary conditions (PBC) is also been implemented by constructing the subsystems in a super cell and employing the Ewald summation and compensation field methods to take the effect of the long-range electrostatic interaction of the crystal environment into account. The PBC-GEBF approach has been used to compute the lattice energies, crystal structures, IR and Raman spectra, and NMR chemical shifts of various condensed-phase systems, including molecular crystals, liquids, ionic liquid crystals, and solutions. Thus, the GEBF and PBC-GEBF approaches are expected to be widely applied to the energies, structures, and molecular properties of a broad range of large systems and condensed-phase systems.