scholarly journals Approaching the Basis Set Limit of CCSD(T) Energies for Large Molecules with Local Natural Orbital Coupled-Cluster Methods

2019 ◽  
Vol 15 (10) ◽  
pp. 5275-5298 ◽  
Author(s):  
Péter R. Nagy ◽  
Mihály Kállay
Keyword(s):  
Basis Set ◽  
Coupled Cluster ◽  
Natural Orbital ◽  
Large Molecules ◽  
Coupled Cluster Methods ◽  
Cluster Methods

scholarly journals Can Popular DFT Approximations and Truncated Coupled Cluster Theory Describe the Potential Energy Surface of the Beryllium Dimer?

2018 ◽  
Vol 71 (10) ◽  
pp. 804 ◽  
Author(s):  
Amir Karton ◽  
Laura K. McKemmish
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Density Functional ◽  
Energy Surface ◽  
Basis Set ◽  
Coupled Cluster ◽  
Good Representation ◽  
Coupled Cluster Methods ◽  
Cluster Methods ◽  
Beryllium Dimer

The potential energy surface (PES) of the ground state of the beryllium dimer poses a significant challenge for high-level ab initio electronic structure methods. Here, we present a systematic study of basis set effects over the entire PES of Be2 calculated at the full configuration interaction (FCI) level. The reference PES is calculated at the valence FCI/cc-pV{5,6}Z level of theory. We find that the FCI/cc-pV{T,Q}Z basis set extrapolation reproduces the shape of the FCI/cc-pV{5,6}Z PES as well as the binding energy and vibrational transition frequencies to within ~10 cm−1. We also use the FCI/cc-pV{5,6}Z PES to evaluate the performance of truncated coupled cluster methods (CCSD, CCSD(T), CCSDT, and CCSDT(Q)) and contemporary density functional theory methods (DFT) methods for the entire PES of Be2. Of the truncated coupled cluster methods, CCSDT(Q)/cc-pV{5,6}Z provides a good representation of the FCI/cc-pV{5,6}Z PES. The GGA functionals, as well as the HGGA and HMGGA functionals with low percentages of exact exchange tend to severely overbind the Be2 dimer, whereas BH&HLYP and M06-HF tend to underbind it. Range-separated DFT functionals tend to underbind the dimer. Double-hybrid DFT functionals show surprisingly good performance, with DSD-PBEP86 being the best performer. Møller–Plesset perturbation theory converges smoothly up to fourth order; however, fifth-order corrections have practically no effect on the PES.

scholarly journals Chemical applications carried out by local pair natural orbital based coupled-cluster methods

2014 ◽  
Vol 43 (14) ◽  
pp. 5032-5041 ◽  
Author(s):  
Manuel Sparta ◽  
Frank Neese
Keyword(s):  
Coupled Cluster ◽  
Accurate Assessment ◽  
Natural Orbital ◽  
Supramolecular Systems ◽  
Coupled Cluster Methods ◽  
Local Pair ◽  
Cluster Methods

Local pair natural orbital coupled-cluster methods are suitable for accurate assessment of the energies of large molecular and supramolecular systems.

scholarly journals Accurate Computation of the Absorption Spectrum of Chlorophyll a with Pair Natural Orbital Coupled Cluster Methods

2020 ◽  
Vol 124 (40) ◽  
pp. 8761-8771 ◽  
Author(s):  
Abhishek Sirohiwal ◽  
Romain Berraud-Pache ◽  
Frank Neese ◽  
Róbert Izsák ◽  
Dimitrios A. Pantazis
Keyword(s):  
Absorption Spectrum ◽  
Chlorophyll A ◽  
Coupled Cluster ◽  
Natural Orbital ◽  
Coupled Cluster Methods ◽  
Accurate Computation ◽  
Cluster Methods

scholarly journals A computational study for the reaction mechanism of metal-free cyanomethylation of aryl alkynoates with acetonitrile

RSC Advances ◽  
2021 ◽  
Vol 11 (30) ◽  
pp. 18246-18251
Author(s):  
Selçuk Eşsiz
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Computational Study ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Metal Free ◽  
Coupled Cluster Methods ◽  
High Level ◽  
Cluster Methods

A computational study of metal-free cyanomethylation and cyclization of aryl alkynoates with acetonitrile is carried out employing density functional theory and high-level coupled-cluster methods, such as [CCSD(T)].

Active-space coupled-cluster methods

2010 ◽  
Vol 108 (21-23) ◽  
pp. 2987-3015 ◽  
Author(s):  
Piotr Piecuch
Keyword(s):  
Coupled Cluster ◽  
Active Space ◽  
Coupled Cluster Methods ◽  
Cluster Methods
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