Rapid computation of intermolecular interactions in molecular and ionic clusters: self-consistent polarization plus symmetry-adapted perturbation theory

Abstract

A method that we have recently introduced for rapid computation of intermolecular interaction energies is reformulated and subjected to further tests. The method employs monomer-based self-consistent field calculations with an electrostatic embedding designed to capture many-body polarization (the "XPol" procedure), augmented by pairwise symmetry-adapted perturbation theory (SAPT) to capture dispersion and exchange interactions along with any remaining induction effects. A rigorous derivation of the XPol+SAPT methodology is presented here, which demonstrates that the method is systematically improvable, and moreover introduces some additional intermolecular interactions as compared to the more heuristic derivation that was presented previously. Applications to various non-covalent complexes and clusters are presented, including geometry optimizations and one-dimensional potential energy scans. The performance of the XPol+SAPT methodology in its present form (based on second-order intermolecular perturbation theory and neglecting intramolecular electron correlation) is qualitatively acceptable across a wide variety of systems-and quantitatively quite good in certain cases-but the quality of the results is rather sensitive to the choice of one-particle basis set. Basis sets that work well for dispersion-bound systems offer less-than-optimal performance for clusters dominated by induction and electrostatic interactions, and vice versa. A compromise basis set is identified that affords good results for both induction and dispersion interactions, although this favorable performance ultimately relies on error cancellation, as in traditional low-order SAPT. Suggestions for future improvements to the methodology are discussed.

Accurate and Efficient Quantum Chemistry Calculations for Noncovalent Interactions in Many-Body Systems: The XSAPT Family of Methods

“…53,88 This is our preferred choice, as it seems physically sound and moreover the use of Mulliken or Loẅdin charges often leads to convergence failure in the XPol procedure, when nonminimal basis sets are employed. 51,88 In any case, the monomer XPol SCF equations (…”

Advances in molecular quantum chemistry contained in the Q-Chem 4 program package

“…Second-order SAPT works well for non-covalent clusters whose interactions are dominated by polarisation (induction) and electrostatics, but inherits MP2's problems with overestimating dispersion energies in the basis-set limit. For dispersion-bound systems, good results are only obtained by carefully choosing a small basis set to exploit error cancellation [319,320].…”

“…A fragment-based method for non-covalent interactions that is currently unique to Q-CHEM is an extended (cluster) version of symmetry-adapted perturbation theory [264,303,304,319,320]. This so-called XSAPT method generalises the traditional SAPT methodology [321] to clusters of arbitrary size, treating many-body polarisation effects in a self-consistent way but approximating other non-covalent interactions (exchange and dispersion) in a pairwise-additive but ab initio fashion.…”

Assessment of hydrophobic interactions and their contributions through the analysis of the methane dimer

“…[42][43][44][45] As QTAIM is based on the topology of the electron density, .ðrÞ, it addresses the interactions between two atoms from a general standpoint [46] which does not depend on the nature of the interaction itself, for example, the presence or abscence of covalency. [56][57][58][59] SAPT is an ab initio method which offers a precise and quantitative description of intermolecular interactions through the decomposition of the interaction energy in electrostatic, induction, dispersion, and exchange components with a specific physical meaning. In addition, the joint study of the reduced density gradient sðrÞ5 jr.ðrÞj 2ð3p 2 Þ 1=3 .…”