Electron correlation, basis sets, and the methylene singlet–triplet gap

1987 ◽  
Vol 86 (2) ◽  
pp. 862-865 ◽  
Author(s):  
Emily A. Carter ◽  
William A. Goddard
Keyword(s):  
Electron Correlation ◽  
Basis Sets

Calculation of the solvation state of organolithium compounds: Effects of basis sets and electron correlation methods

2009 ◽  
Vol 109 (1) ◽  
pp. 34-42 ◽  
Author(s):  
Lawrence M. Pratt ◽  
Darrel Jones ◽  
Andrea Sease ◽  
Donta Busch ◽  
Emmanuel Faluade ◽  
...  
Keyword(s):  
Electron Correlation ◽  
Basis Sets ◽  
Solvation State ◽  
Organolithium Compounds ◽  
Correlation Methods

Theoretical study on the insertion reaction of CH(X2Π) with CH4

1997 ◽  
Vol 75 (7) ◽  
pp. 996-1001 ◽  
Author(s):  
Zhi-Xiang Wang ◽  
Ming-Bao Huang. ◽  
Ruo-Zhuang Liu
Keyword(s):  
Electron Correlation ◽  
Energy Surface ◽  
Theoretical Study ◽  
Reaction Path ◽  
Basis Sets ◽  
Insertion Reaction ◽  
Molecular Orbital Calculations ◽  
Insertion Reactions ◽  
Moller Plesset ◽  
Ch Radical

The CH + CH4 reaction has been studied by means of ab initio molecular orbital calculations incorporating electron correlation with Møller–Plesset perturbation theory up to second and fourth orders with the 6-31G(d,p) and 6-311++G(2d,p) basis sets. An energetically feasible insertion reaction path has been found in the potential energy surface that confirms the experimental proposal for the mechanism of the CH + CH4 reaction. The feature of the mechanism for the CH + CH4 insertion reaction is found to be different from the feature of the mechanisms for the CH + NH3, CH + H2O, and CH + HF insertion reactions, but somewhat similar to that for the CH2 + CH4 insertion reaction. Energetic results for the CH + CH4 reactions are in agreement with experiment. Keywords: CH radical, methane, reaction mechanism.

Do the mercaptocarbene (H–C–S–H) and selenocarbene (H–C–Se–H) congeners of hydroxycarbene (H–C–O–H) undergo 1,2-H-tunneling?

2011 ◽  
Vol 76 (6) ◽  
pp. 645-667 ◽  
Author(s):  
János Sarka ◽  
Attila G. Császár ◽  
Peter R. Schreiner
Keyword(s):  
Electron Correlation ◽  
Reaction Path ◽  
Focal Point ◽  
Structural Data ◽  
Basis Sets ◽  
Stationary Points ◽  
One Dimensional ◽  
Point Analysis ◽  
Uncertainty Estimates

The principal purpose of this investigation is the determination of the tunneling half-lives of the trans-HCSH → H2CS and the trans-HCSeH → H2CSe unimolecular isomerization reactions at temperatures close to 0 K. To aid these determinations, accurate electronic structure computations were performed, with electron correlation treatments as extensive as CCSDT(Q) and basis sets as large as aug-cc-pCV5Z, for the isomers of [H,H,C,S] and [H,H,C,Se] on their lowest singlet surfaces and for the appropriate transition states yielding structural data for key stationary points characterizing the isomerization reactions. The computational results were subjected to a focal-point analysis (FPA) that yields accurate relative energies with uncertainty estimates. The tunneling half-lives were determined by a simple Eckart-barrier approach and via the more sophisticated though still one-dimensional Wentzel–Kramers–Brillouin (WKB) approximation. Only stationary-point information is needed for the former while an intrinsic reaction path (IRP) is necessary for the latter approach. Both protocols suggest that, unlike for the parent hydroxymethylene (HCOH), at the low temperatures of matrix isolation experiments no tunneling will be observable for the trans-HCSH and trans-HCSeH systems.

A comparative study of the energetics, structures, and mechanisms of the HCN ↔ HNC and LiCN ↔ LiNC isomerizations

1996 ◽  
Vol 74 (6) ◽  
pp. 1072-1077 ◽  
Author(s):  
V. Sreedhara Rao ◽  
Amrendra Vijay ◽  
A.K. Chandra
Keyword(s):  
Potential Energy ◽  
Electron Correlation ◽  
Potential Energy Surfaces ◽  
Basis Sets ◽  
Ab Initio Theory ◽  
Molecular Bond ◽  
Bond Rearrangement ◽  
Energy Surfaces ◽  
Isomerization Processes ◽  
Rearrangement Processes

The potential energy surfaces of the HCN ↔ HNC and LiCN ↔ LiNC isomerization processes were determined by ab initio theory using fully optimized triple-zeta double polarization types of basis sets. Both the MP2 corrections and the QCISD level of calculations were performed to correct for the electron correlation. Results show that electron correlation has a considerable influence on the energetics and structures. Analysis of the intramolecular bond rearrangement processes reveals that, in both cases, H (or Li+) migrates in an almost elliptic path in the plane of the molecule. In HCN ↔ HNC, the migrating hydrogen interacts with the in-plane π,π* orbitals of CN, leading to a decrease in the C—N bond order. In LiCN ↔ LiNC, Li+ does not interact with the corresponding π,π* orbitals of CN. Key words: potential energy surfaces, intra-molecular bond rearrangement, bond orders, elliptic path, migration of Li+.

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