نتایج جستجو برای: ccsd

تعداد نتایج: 1108  

Journal: :Monthly Notices of the Royal Astronomical Society 2022

Abstract Only 4 of the diffuse interstellar bands (DIBs) are currently accounted for, ascribed to electronic transitions C$_{60}^+$. Investigations into carriers other DIBs historically focus on charged and neutral hydrocarbons, little information is available regarding oxygenated carbon hydrocarbon species that result from two most abundant heavy elements in medium, C O. In this study, we asse...

Journal: :Journal of computational chemistry 2005
A. Patrícia Bento Miquel Solà F. Matthias Bickelhaupt

To obtain a set of consistent benchmark potential energy surfaces (PES) for the two archetypal nucleophilic substitution reactions of the chloride anion at carbon in chloromethane (S(N)2@C) and at silicon in chlorosilane (S(N)2@Si), we have explored these PESes using a hierarchical series of ab initio methods [HF, MP2, MP4SDQ, CCSD, CCSD(T)] in combination with a hierarchical series of six Gaus...

Journal: :The Journal of chemical physics 2008
Hui Li Tsuneo Hirano Takayoshi Amano Robert J Le Roy

To obtain theoretical insight regarding the stability and formation dynamics of the interstellar ions HCO(+) and HOC(+), stationary points and the associated vibrational frequencies on the full nine-dimensional potential energy surface for the electronic ground state have been calculated using coupled-cluster theory with both single and double substitutions (CCSD). The energetics were refined w...

2017
Kayahan Saritas Jeffrey C. Grossman

We investigate the isomerization enthalpy of the Dihydroazulene/Vinylheptafulvene (DHA/VHF) molecular photoswitch system derivatives using electronic structure calculation methods including Density Functional Theory (DFT), Quantum Monte Carlo (QMC) and Coupled Cluster (CCSD(T)). Recent efforts have focused on tuning the isomerization enthalpy of the photoswitch for solar thermal energy storage ...

Journal: :Physical chemistry chemical physics : PCCP 2014
Jan-M Mewes Vladimir Jovanović Christel M Marian Andreas Dreuw

In this work, we present a complete mechanistic picture of the non-radiative decay of the mono-substituted aromatic compound nitrobenzene from the bright singlet state to the electronic ground state. This mechanism involves internal conversion (IC) and inter-system crossing (ISC) along three dominating internal coordinates of the nitro group and consistently explains the experimental findings. ...

Journal: :The journal of physical chemistry. A 2009
Desiree M Bates Gregory S Tschumper

MP2 and CCSD(T) complete basis set (CBS) limit relative electronic energies (DeltaE(e)) have been determined for eight low-lying structures of the water hexamer by combining explicitly correlated MP2-R12 computations with higher-order correlation corrections from CCSD(T) calculations. Higher-order correlation effects are quite substantial and increase DeltaE(e) by at least +0.19 kcal mol(-1) an...

Journal: :The Journal of organic chemistry 2010
Rainer Glaser Jian Yin Stephanie Miller

The uncatalyzed, thermal N-inversion reactions were studied of pyrimidin-4(3H)-imine (PMI), pyridin-2(1H)-imine (PYI), and 1H-purine-6(9H)-imine (PUI). Relevant regions of the potential energy surfaces were explored with second-order Moller-Plesset perturbation theory (MP2(full)/6-31G(d)) and with coupled cluster theory (CCSD/6-31G(d), CCSD/6-31+G(d)). The thermochemistry of stationary structur...

Journal: :Physical chemistry chemical physics : PCCP 2016
Brina Brauer Manoj K Kesharwani Sebastian Kozuch Jan M L Martin

The S66x8 dataset for noncovalent interactions of biochemical relevance has been re-examined by means of MP2-F12 and CCSD(F12*)(T) methods. We deem our revised benchmark data to be reliable to about 0.05 kcal mol(-1) RMS. Most levels of DFT perform quite poorly in the absence of dispersion corrections: somewhat surprisingly, that is even the case for the double hybrids and for dRPA75. Analysis ...

Journal: :The Journal of chemical physics 2016
Wendell W Walters Greg Michalski

Ab initio calculations have been carried out to investigate nitrogen (k15/k14) and position-specific oxygen (k17/k16O & k18/k16) kinetic isotope effects (KIEs) for the reaction between NO and O3 using CCSD(T)/6-31G(d) and CCSD(T)/6-311G(d) derived frequencies in the complete Bigeleisen equations. Isotopic enrichment factors are calculated to be -6.7‰, -1.3‰, -44.7‰, -14.1‰, and -0.3‰ at 298 K f...

Journal: :Journal of computational chemistry 2009
Yun-Xiang Lu Jian-Wei Zou Ji-Cai Fan Wen-Na Zhao Yong-Jun Jiang Qing-Sen Yu

A systematic theoretical investigation on a series of dimeric complexes formed between some halocarbon molecules and electron donors has been carried out by employing both ab initio and density functional methods. Full geometry optimizations are performed at the Moller-Plesset second-order perturbation (MP2) level of theory with the Dunning's correlation-consistent basis set, aug-cc-pVDZ. Bindi...

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