Interaction energies computed with HFLD typically lie between those computed at the CCSD and CCSD(T) levels of theory. (88) On various closed-shell benchmark sets for NCIs, this approach typically provides sub-kcal/mol accuracy, as demonstrated on noble-gas dimers, as well as on the S66, (89) L7, (90) and LP14 (83) benchmark sets. (75−77,79) By exploiting the multilevel implementation of the DLPNO-CCSD(T) method, (87) one can solve the coupled-cluster equations while neglecting the nondispersive excitations, which leads to a cost-effective LD-corrected HF method called HFLD. Importantly, the LED methodology can be used to identify the “dispersion excitations” in the DLPNO-CCSD correlation energy.
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(78) For these reasons, the DLPNO-CCSD(T)/LED methodology has found widespread applications in the study of intermolecular interactions. These terms were found to correlate reasonably well with those obtained using SAPT, especially in the weak-interaction limit. (75−77) This scheme decomposes the DLPNO-CCSD(T) interaction energy into physically meaningful fragment-pairwise energy terms, such as electrostatics, exchange, electronic preparation, LD, and nondispersive correlation. In addition, the DLPNO-CCSD(T) approach can be combined with the well-established local energy decomposition (LED) scheme for the study of NCIs. For relative energies, it reproduces the results of its canonical parent method within 1 kJ/mol when used in conjunction with the recently devised “complete PNO space” (CPS) extrapolation scheme, CPS(6/7), (74) as shown on the most challenging sets of GMTKN55 (30) benchmark superset. (61−70) It combines great efficiency (70−73) with essentially canonical CCSD(T) accuracy. (59−61) Among them, the domain-based local pair natural orbital CCSD(T) method, i.e., DLPNO-CCSD(T), has proven instrumental in a large number of chemical applications. (58) By exploiting the rapid decay of electron correlation with the interelectronic distance, low scaling local variants of this approach have been developed. In particular, the coupled-cluster method with singles, doubles, and perturbative treatment of triple excitations, i.e., CCSD(T), is known to provide extremely accurate results for a broad range of different chemical systems. Unlike mean-field theories, correlated wave function-based methods naturally describe LD and can thus be used for computing NCI energies accurately within a supermolecular approach. (40,41) VV10 is included in “combinatorially” optimized exchange-correlation functionals, such as B97M-V, (42) ωB97M-V, (43) and ωB97X-V, (44) and it is also used in the so-called HF-NL and DFT-NL methods. (35−37) Finally, vdW-density functional (vdW-DF) (38,39) methods include a density-dependent term, e.g., the VV10 nonlocal (NL) correlation functional that accounts for the dispersion energy.
Gaussian software hartree fock method free#
A conceptually similar approach to DFT-D is the Tkatchenko–Scheffler (TS) scheme, (35) which relies on reference data for the free atoms for the calculation of the dispersion correction. (27−30) The efficient small basis set composite “3c” variants of such approaches, namely, HF-3c (17) and DFT-3c ( e.g., B97–3c, PBEh-3c, HSE-3c, and r 2SCAN-3c) (31−34) methods, include additional geometrical counterpoise and short-range basis set incompleteness corrections. (22−26) Alternatively, force field-like dispersion correction terms are added on top of the HF and DFT energies, as it is done in the popular HF-D or DFT-D method of Grimme and co-workers.
For example, several Minnesota functionals have been internally parameterized to approximately account for LD effects.
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