Characterizing a nonclassical carbene with coupled cluster methods: cyclobutylidene

2016 ◽  
Vol 18 (35) ◽  
pp. 24560-24568 ◽  
Author(s):  
Xiao Wang ◽  
Jay Agarwal ◽  
Henry F. Schaefer III
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Coupled Cluster ◽  
Reaction Paths ◽  
Coupled Cluster Methods ◽  
Kinetic Rates ◽  
Reaction Barriers ◽  
Cluster Methods

Cyclobutylidene is a nonclassical compound that undergoes rapid rearrangement. Three reaction paths on the lowest potential energy surface are examined with theory; reaction barriers and kinetic rates are reported, among other analyses.

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.

A Multireference Coupled-Cluster Potential Energy Surface of Diazomethane, CH2N2

2005 ◽  
Vol 109 (44) ◽  
pp. 10148-10152 ◽  
Author(s):  
Ioannis S. K. Kerkines ◽  
Petr Čársky ◽  
Aristides Mavridis
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Coupled Cluster

scholarly journals Revisiting the F + HCl → HF + Cl reaction using a multireference coupled-cluster method

2016 ◽  
Vol 18 (44) ◽  
pp. 30241-30253 ◽  
Author(s):  
Yuri Alexandre Aoto ◽  
Andreas Köhn
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Excellent Agreement ◽  
Rate Constant ◽  
Energy Surface ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Coupled Cluster Method ◽  
Title Reaction

A potential energy surface for the title reaction is constructed using a multireference coupled-cluster method, giving rate constant in excellent agreement with experiments.

Accurate characterization of the lowest triplet potential energy surface of SO2 with a coupled cluster method

2019 ◽  
Vol 150 (14) ◽  
pp. 144303
Author(s):  
Praveen Kumar ◽  
Jacek Kłos ◽  
Bill Poirier ◽  
Millard H. Alexander ◽  
Hua Guo
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Coupled Cluster Method
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