How Should We Calculate Transition State Geometries for Radical Reactions? The Effect of Spin Contamination on the Prediction of Geometries for Open-Shell Saddle Points

2000 ◽  
Vol 104 (3) ◽  
pp. 446-450 ◽  
Author(s):  
Yao-Yuan Chuang ◽  
Elena L. Coitiño ◽  
Donald G. Truhlar
Keyword(s):  
Transition State ◽  
Saddle Points ◽  
Open Shell ◽  
Radical Reactions ◽  
Spin Contamination

Probing the relationship between spin contamination and first hyperpolarizability: Open-shell Möbius anion

2014 ◽  
Vol 114 (11) ◽  
pp. 720-724 ◽  
Author(s):  
Ying Gao ◽  
Hong-Liang Xu ◽  
Rong-Lin Zhong ◽  
Shi-Ling Sun ◽  
Zhong-Min Su
Keyword(s):  
Open Shell ◽  
First Hyperpolarizability ◽  
Spin Contamination ◽  
The Relationship

Transition State and G2Q Analysis of Hydrocarbon Radical Reactions with Cl2

1995 ◽  
Vol 34 (12) ◽  
pp. 4202-4211 ◽  
Author(s):  
Max Markus Tirtowidjojo ◽  
Brenda Thies Colegrove ◽  
Joseph L. Durant
Keyword(s):  
Transition State ◽  
Radical Reactions ◽  
Hydrocarbon Radical

Quantum chemical modelling of reactions in hydrocarbon combustion. Study of the CH4 + O2 reactions

1984 ◽  
Vol 49 (6) ◽  
pp. 1440-1447 ◽  
Author(s):  
Ján Urban ◽  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Rate Constants ◽  
Quantum Chemical ◽  
Transition State Theory ◽  
Saddle Points ◽  
State Theory ◽  
Relative Probability ◽  
Hydrocarbon Combustion ◽  
Chemical Modelling

The rate constants of two alternative reactions, i.e CH4 + O2 → CH2 + H2O2 and CH4 + O2 → CH3 + HOO have been studied by the ab initio and MINDO/3 methods. A preliminary appreciation of the used methods has been done with a selected set of carbene reactions. The characteristics of minima as well as the saddle points on the corresponding reaction paths of both reactions have been found. The discussion of the relative probability of a pathway of the above-mentioned reactions is based on the rate constants determined by the use of transition state theory.

Saddle-point geometries and barriers to internal rotation of formamide : an ab initio study

1980 ◽  
Vol 33 (2) ◽  
pp. 249 ◽  
Author(s):  
L Radom ◽  
NV Riggs
Keyword(s):  
Transition State ◽  
Ground State ◽  
Energy Surface ◽  
Saddle Points ◽  
Geometry Optimization ◽  
Internal Motion ◽  
Basis Set ◽  
Minimal Basis ◽  
Experimental Values ◽  
Extended Basis

By use of a direct transition-state program and the STO-3G minimal basis set, two saddle-points are detected on the energy surface for internal motion of formamide. These correspond mainly to rotation about the C-N bond along with some lengthening of this bond and increased pyramidal distortion at nitrogen as compared with that in the ground state. The STO-3G estimates of the barrier height (34-39 kJ mol-1) are in very poor agreement with experimental values (70-90 kJ mol-1), but 4- 31G energy evaluations for the STO-3G-optimized structures give much better estimates (62-80 kJ mol-1). Contrary to a previous report, use of the 4-31G extended basis set for geometry optimization suggests that only the lower-energy member (NH2 cis to CO) of the above pair is a true transition state for internal motion of formamide; its energy relative to that of the 4-31G-optimized ground state (planar) is 83.5 kJ mol-1, very close to the midpoint of the experimental range. The transition state appears to lie in a region of the 4-31G energy surface that is relatively flat with respect to pyramidal distortion at nitrogen; constraining the amino group to planarity raises the calculated energy by only 6.5kJmol-1.

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