Andreas Köhn

TL;DR: In this article, the second-order Moller-Plesset perturbation theory (MP2) correlation energy with the cardinal number X is investigated for the correlation consistent basis-set series cc-pVXZ and cc-PV(X+d)Z.

TL;DR: Explicitly Correlated Electrons in Molecules Christof Hattig, Wim Klopper,* Andreas K€ohn, and David P. Tew Lehrstuhl.

TL;DR: Molpro as mentioned in this paper is a general purpose quantum chemistry software package with a long development history, originally focused on accurate wavefunction calculations for small molecules but now has many additional distinctive capabilities that include, inter alia, local correlation approximations combined with explicit correlation, highly efficient implementations of single-reference correlation methods, robust and efficient multireference methods for large molecules, projection embedding, and anharmonic vibrational spectra.

TL;DR: In this article, an implementation of transition moments and excited-state first-order properties for the approximate coupled-cluster singles-and-doubles model (CC2) using the resolution of the identity (RI) approximation is reported.

TL;DR: In this paper, the derivation and implementation of excited state gradients are reported for the approximate coupled-cluster singles and doubles model CC2 employing the resolution-of-the-identity approximation for electron repulsion integrals.