Generalized energy-based fragmentation approach for modeling condensed phase systems

to condensed phase systems with periodic boundary condition (PBC). The socalled PBC-GEBF method provides an alternative way of calculating electronic structures of condensed phase systems, whose accuracy is comparable to standard periodic electronic structure methods for some types of condensed phase systems such as molecular crystals and ionic liquid crystals. Within the PBCGEBF approach, the unit cell energy (or properties) of a condensed phase system can be evaluated as a linear combination of ground-state energies (or corresponding properties) of a series of electrostatically embedded subsystems, which can be routinely calculated with existing molecular quantum chemistry packages. With the PBC-GEBF approach, one can routinely perform ab initio calculations at post-Hartree-Fock levels, including Moller-Plesset perturbation theory (MP2) or coupled cluster singles and doubles, on certain types of condensed phase systems, in which periodic post-Hartree-Fock methods are not available or not feasible computationally. This review will offer an overview of the methodology and implementation of the PBC-GEBF method and its applications in predicting the structures, lattice energies, and vibrational spectra of a wide range of molecular and ionic liquid crystals. Our results show that the PBC-GEBF approach at post-Hartree-Fock theory level can generally provide highly accurate descriptions on the structure and properties of crystals under study. For example, the vibrational spectra of the crystalline BH3NH3 predicted by the PBC-GEBF approach at the MP2 level are in better agreement with the experimentally observed spectra, than those based on density functional theory calculations. (C) 2017 John Wiley & Sons, Ltd