Local coupled-cluster singles–doubles theory (LCCSD) is a theorist’s attempt to capture electron–electron correlation in a fast amount of time and with chemical accuracy. Many of the difficult computational hurdles have been navigated over the last twenty years, including how to construct a linear scaling algorithm and how to produce smooth potential energy surfaces. Nevertheless, there remains...

We present an implementation of the equation motion coupled-cluster singles and doubles (EOM-CCSD) theory using periodic boundary conditions a plane wave basis set. Our EOM-CCSD is applied to study F-centers in alkaline earth oxides employing supercell approach. The convergence calculated electronic excitation energies for neutral color centers MgO, CaO, SrO crystals with respect orbital set sy...

Diffusion Monte Carlo (DMC) calculations are performed on the monocyclic and bicyclic forms of m-benzyne, which are the equilibrium structures at the CCSD(T) and CCSD levels of coupled cluster theory. We employed multiconfiguration self-consistent field trial wave functions which are constructed from a carefully selected eight-electrons-in-eight-orbitals complete active space [CAS(8,8)], with c...

An efficient and highly vectorized implementation of the coupled cluster singles and doubles ~CCSD! model using a direct atomic integral technique is presented. The minimal number of n processes has been implemented for the most time consuming terms and point group symmetry is used to further reduce operation counts and memory requirements. The significantly increased application range of the C...

The structure of the calix[4]arene(C4A)-Ar(n) complexes has been investigated by laser induced fluorescence spectroscopy, mass-selected resonant two-color two-photon ionization (2C-R2PI) spectroscopy, fragment detected IR photodissociation (FDIRPD) spectroscopy, and high level first principles electronic structure calculations at the MP2 and CCSD(T) levels of theory. C4A has a very high ability...

The catalysis of the Hajos–Parrish reaction by cis - and trans -4,5-ethano-proline was explored experimentally computationally with DFT (?B97X-D MN15) DLPNO-CCSD(T).

We extend our recently published short-range gradient-corrected density functional from the closed-shell to the open-shell case, combine it with long-range coupled-cluster methods (CCSD, CCSD(T)), and apply it to the weakly bound alkali-metal rare-gas dimers AmRg (Am = Li–Cs; Rg = Ne–Xe). The results are shown to be superior, with medium-size basis sets, to pure DFT and pure coupled-cluster cal...

Stationary points for four geometrically different states of methylene: bent and linear triplet methylene, bent and linear singlet methylene were investigated using the highly reliable post-HF CCSD(T) method. Extrapolations to the CCSD(T) basis set (CBS) limit from Dunning triple to quintuple correlation consistent polarized basis sets were performed for total energies, for the equilibrium CH d...

The 1Lb and 1La excited states of naphthols are characterized by using time-dependent density functional theory (TDDFT), configuration interaction with singles (CIS), and equation-of-motion coupled cluster singles and doubles (EOM-CCSD) methods. TDDFT fails dramatically at predicting the energy and ordering of the 1La and 1Lb excited states as observed experimentally, while EOM-CCSD accurately ...