Speaker: Prof. Stefan Grimme
Mulliken Center for Theoretical Chemistry, Clausius Institute for Physical and Theoretical Chemistry, University of Bonn, Beringstraße 4, 53115 Bonn, Germany
Title: New ’low-cost’ electronic structure methods for large systems
Abstract: Recently we introduced a new, special purpose tight-binding (TB) electronic structure Hamiltonian termed PTB[1] which is expressed in an accurate polarized valence double-zeta AO basis set (vDZP). The basis set has been specially optimized in molecular DFT calculations using standard ECPs for all elements up to radon[2]. The combination of the accurate wB97X(-V)[3] RSH functional with vDZP/ECP and an adjusted D4 dispersion correction defines a new member in our hierarchy of efficient composite electronic structure methods, termed wB97X-3c[2]. This basis set optimization concept is furthermore applied to a minimal set of AOs which — as a totally new ingredient — is made adaptive, i.e., radially different for symmetry distinct atoms in a molecule. The "breathing" of the AOs in the molecular environment is parameterized efficiently by on-the-fly computed effective atomic charges and coordination numbers. This so-called qvSZP set[4] provides in typical DFT applications results of about or better than DZ quality. It forms the basis of our third-generation tight-binding model GP3-xTB[5] which includes nonlocal Fock-exchange as well as other new, many-center Hamiltonian terms (e.g., atomic correction potentials, ACP). It aims at general purpose (GP) applicability in chemistry and more closely approaches DFT accuracy (actually wB97X-D4/TZ) than previous semi-empirical methods at only slightly increased computational cost (factor of 1.5-3 compared to GFN2-xTB). The talk describes key improvements of the underlying TB theory as well as extensive benchmarking on a wide range of standard test sets.
[1] S. Grimme, M. Müller, A. Hansen, J. Chem. Phys., 158 (2023), 124111.
[2] M. Müller, A. Hansen, S. Grimme, J. Chem. Phys. 158 (2023), 014103
[3] N. Mardirossian and M. Head-Gordon, Phys. Chem. Chem. Phys. 16 (2016), 9904.
[4] M. Müller, A. Hansen, S. Grimme, J. Chem. Phys. 159 (2023), 164108 [5] S. Grimme, T. Froitzheim, M. Müller, A. Hansen, to be published.