Communication: Improved pair approximations in local coupled-cluster methods

From plane waves to local Gaussians for the simulation of correlated periodic systems

“…In the future, this infrastructure will be combined with other correlated methods, including coupled-cluster and F12 methods 4,8,9,49,63,64 . Furthermore, methods which directly exploit the locality of correlation effects, including quantum cluster methods such as dynamical meanfield theory 65 and density matrix embedding theory [66][67][68][69] , as well as more traditional domain-based approaches to local correlation 25,36,70 can be used within this framework, and are being actively explored.…”

Communication: Multipole approximations of distant pair energies in local correlation methods with pair natural orbitals

“…The approximated distant pair energies are summed up to yield the total distant correlation energy E sc dist , which is added to the final LMP2 energy. This approach has been used in the PNO-LMP2 and PNO-LCCSD (local coupled-cluster with singles and doubles) methods of Riplinger et al 9,10 and ours, [11][12][13] as well as in recent PNO-NEVPT2 14 and PNO-CASPT2 15 methods. In all these works, only the semi-canonical dipole-dipole approximation was employed.…”

“…1 which has been used in previous benchmarks of PNO-LCCSD methods. 12,16 This is an excellent and difficult benchmark case since the correlation effects on the reaction energy are very large (Hartree-Fock, LMP2-F12, and LCCSD-F12 yield 92, 251, and 190 kJ mol −1 , respectively, using the VTZ-F12 basis set 16 ). The results can be directly compared to an experimental gas-phase value 17 of 196.5 ± 11.2 kJ/mol, which has been obtained by subtracting the PW91/cc-pVTZ-pp zero-point correction 17 of −8.2 kJ/mol from the measured value.…”

Experimental and Theoretical Determination of Dissociation Energies of Dispersion-Dominated Aromatic Molecular Complexes

“…LCC methods rely on pair and domain approximations, and in particular the pair approximation has recently received attention with respect to its application to long-range intermolecular interactions. [90][91][92] The pair approximation depends on the distance between localized occupied orbitals, and for weak intermolecular interactions, it is crucial to compute the more distant pairs (also) accurately. [90][91][92] LCC methods have been improved by introducing pair (or pseudo) natural orbitals (PNO) in conjunction with domain approximations.…”

“…[90][91][92] The pair approximation depends on the distance between localized occupied orbitals, and for weak intermolecular interactions, it is crucial to compute the more distant pairs (also) accurately. [90][91][92] LCC methods have been improved by introducing pair (or pseudo) natural orbitals (PNO) in conjunction with domain approximations. [93][94][95][96][97][98] Some recent applications to large systems, including the S66 test set, 99,100 can be found in Refs.…”