THEORETICAL STUDIES ON BOND DISSOCIATION ENERGIES FOR SOME THIOL COMPOUNDS BY DENSITRY FUNCTIONAL THEORY AND CBS-Q METHOD

2008 ◽  
Vol 07 (05) ◽  
pp. 943-951 ◽  
Author(s):  
XIAO-HONG LI ◽  
ZHENG-XIN TANG ◽  
ABRAHAM F. JALBOUT ◽  
XIAN-ZHOU ZHANG ◽  
XIN-LU CHENG
Keyword(s):  
Density Functional ◽  
Computational Cost ◽  
Basis Set ◽  
Basis Sets ◽  
Q Method ◽  
Bond Dissociation Energies ◽  
Functional Theory ◽  
Thiol Compounds ◽  
Bond Dissociation ◽  
Dissociation Energies

Quantum chemical calculations are used to estimate the bond dissociation energies (BDEs) for 15 thiol compounds. These compounds are studied by employing the hybrid density functional theory (B3LYP, B3PW91, B3P86, PBE0) methods and the complete basis set (CBS-Q) method together with 6-311G** basis set. It is demonstrated that B3P86 and CBS-Q methods are accurate for computing the reliable BDEs for thiol compounds. In order to test whether the non-local BLYP method suggested by Fu et al.19 is general for our study and whether B3P86 method has a low basis set sensitivity, the BDEs for seven thiol compounds are also calculated using BLYP/6-31+G* and B3P86 method with 6-31+G*, 6-31+G**, and 6-311+G** basis sets for comparison. The obtained results are compared with the available experimental results. It is noted that B3P86 method is not sensitive to the basis set. Considering the inevitable computational cost of CBS-Q method and the reliability of the B3P86 calculations, B3P86 method with a moderate or a larger basis set may be more suitable to calculate the BDEs of the C–SH bond for thiol compounds.

THEORETICAL STUDIES ON BOND DISSOCIATION ENERGIES FOR SOME ALIPHATIC ALCOHOL COMPOUNDS BY DENSITY FUNCTIONAL THEORY AND CBS-Q METHOD

2011 ◽  
Vol 10 (02) ◽  
pp. 179-189 ◽  
Author(s):  
XIAO-HONG LI ◽  
GENG-XIN YIN ◽  
XIAN-ZHOU ZHANG
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Aliphatic Alcohol ◽  
Basis Set ◽  
Basis Sets ◽  
Q Method ◽  
Bond Dissociation Energies ◽  
Functional Theory ◽  
Bond Dissociation ◽  
Dissociation Energies

Quantum chemical calculations are used to estimate the bond dissociation energies (BDEs) for 20 aliphatic alcohol compounds. These compounds are studied by employing the hybrid density functional theory (B3LYP, B3PW91, and B3P86) methods with 6-311G** basis set and the complete basis set (CBS-Q) method together. It is demonstrated that B3P86 and CBS-Q methods are accurate to compute the reliable BDEs for aliphatic alcohol compounds. In order to test whether the non-local BLYP method suggested by Jursic18 is general for our study and whether B3P86 method has a low basis set sensitivity, the BDEs for 20 aliphatic alcohol compounds are also calculated using BLYP/6-31+G*, BLYP/6-31G*, and B3P86 methods with 6-31G*, 6-31+G*, and 6-31G** basis sets for comparison. The obtained results are compared with the available experimental results. It is noted that B3P86 method is sensitive to the basis sets. Considering the inevitably computational cost of CBS-Q method and the reliability of the B3P86 calculation, B3P86 method with 6-31G** basis set may be more suitable to calculate the BDEs of the C–O bond for aliphatic alcohol compounds.

THEORETICAL STUDIES ON HEATS OF FORMATION FOR SOME THIOL COMPOUNDS BY DENSITY FUNCTIONAL THEORY AND CBS-Q METHOD

2007 ◽  
Vol 06 (04) ◽  
pp. 675-685 ◽  
Author(s):  
XIAO-HONG LI ◽  
RUI-ZHOU ZHANG ◽  
XIAN-ZHOU ZHANG ◽  
XIN-LU CHENG ◽  
XIANG-DONG YANG
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Cost ◽  
Basis Set ◽  
Heats Of Formation ◽  
Basis Sets ◽  
Q Method ◽  
Functional Theory ◽  
Thiol Compounds ◽  
Error Bar

The heats of formation (HOFs) for 15 thiol compounds are calculated by employing the hybrid density functional theory (B3LYP, B3PW91, B3P86) methods with 6-311G** basis set and the complete basis set (CBS-Q) method. It is demonstrated that the B3P86 and CBS-Q methods are accurate to compute the reliable HOFs for thiol compounds. In order to test whether the B3P86 method has a low basis set sensitivity, the HOFs for six thiol compounds are also calculated by using the B3P86 method with 6-31+G*, 6-31+G**, and 6-311+G** basis sets for comparison. We also extend our study by employing the nonlocal BLYP method together with 6-31+G* basis set to calculate the HOFs for thiol compounds. The obtained results are compared with the experimental results. It is noted that the B3P86 method is not sensitive to the basis sets. Considering the inevitably computational cost of CBS-Q method and the reliability of the B3P86 calculation, the B3P86 method with a moderate or a larger basis set such as 6-311G** and 6-311+G** may be more suitable to calculate the HOFs of thiol compounds. In addition, we believe that the maximum error associated with the calculated HOFs is less than 6 kcal/mol for the B3P86/6-311G** method and it is expected that the error bar is more likely 1–5 kcal/mol for the HOFs of thiol compounds.

Assessment of PBE0 Calculation of C-NO2 Bond Dissociation Energies for Nitroaromatic System

2014 ◽  
Vol 915-916 ◽  
pp. 675-678
Author(s):  
Xin Fang Su ◽  
Wei Huang ◽  
Hai Ying Wu
Keyword(s):  
Density Functional ◽  
Molecular System ◽  
Absolute Error ◽  
Basis Sets ◽  
Bond Dissociation Energies ◽  
Average Absolute Error ◽  
Functional Theory ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Experimental Values

Density functional theory (DFT) is used to calculate the C-NO2bond dissociation energies (BDEs) in nitrobenzene; 3-amino-nitrobenze; 4-amino-nitrobenze; 1,3-dinitrobenzene; 1,4-dinitrobenzene; 2-methyl-nitrobenzene; 4-methyl-nitrobenzene and 1,3,5-trinitrobenzene nitroaromatic molecular system. B3P86 and PBE0 methods in combination with 6-31G** and 6-311G** basis sets are employed. Comparison between the computational results and the experimental values reveals that the calculated C-NO2bond BDEs can be improved from B3P86 to PBE0 functional. Level of theory employing PBE0/6-311G** is found to be sufficiently reliable to compute BDEs of C-NO2bond for nitroaromatic molecules with an average absolute error of 0.98 kcal mol-1.

The Theory Investigation for the Antioxidant Activity of Phloretin: A Comparation with Naringenin

2014 ◽  
Vol 513-517 ◽  
pp. 359-362
Author(s):  
Ming Xun Yan ◽  
Jin Dong Gong ◽  
Ping Shen ◽  
Chang Ying Yang
Keyword(s):  
Density Functional Theory ◽  
Antioxidant Activity ◽  
Density Functional ◽  
Radical Scavenging ◽  
Basis Set ◽  
Hydroxyl Groups ◽  
Bond Dissociation Energies ◽  
Functional Theory ◽  
Dissociation Energies ◽  
Radical Scavenging Properties

Density functional theory (DFT) calculations, based on B3LYP/6-311G (d, p) basis set, were performed to evaluate the OH bond dissociation energies (BDEs) for phloretin, compared with naringenin, in order to assess the contribution of hydroxyl groups at different position to the radical-scavenging properties. It is indicated clearly that A6 OH is determined as the weakest O-H bond, give rise to the smallest BDE, 73.98 kcal/mol. BDE of B4 OH decreases 2.5 kcal/mol in benzene, very close to that of A6OH, indicated that B4 OH group is also mainly contributed to the reaction with free radicals, especially in non-polar environments.

scholarly journals An Accurate and Efficient Method to Predict Y-NO Bond Homolysis Bond Dissociation Energies

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Hong Zhi Li ◽  
Lin Li ◽  
Zi Yan Zhong ◽  
Yi Han ◽  
LiHong Hu ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Molecular Descriptors ◽  
Basis Set ◽  
Bond Dissociation Energies ◽  
Data Set ◽  
Test Set ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Bond Homolysis

The paper suggests a new method that combines the Kennard and Stone algorithm (Kenstone, KS), hierarchical clustering (HC), and ant colony optimization (ACO)-based extreme learning machine (ELM) (KS-HC/ACO-ELM) with the density functional theory (DFT) B3LYP/6-31G(d) method to improve the accuracy of DFT calculations for the Y-NO homolysis bond dissociation energies (BDE). In this method, Kenstone divides the whole data set into two parts, the training set and the test set; HC and ACO are used to perform the cluster analysis on molecular descriptors; correlation analysis is applied for selecting the most correlated molecular descriptors in the classes, and ELM is the nonlinear model for establishing the relationship between DFT calculations and homolysis BDE experimental values. The results show that the standard deviation of homolysis BDE in the molecular test set is reduced from 4.03 kcal mol−1calculated by the DFT B3LYP/6-31G(d) method to 0.30, 0.28, 0.29, and 0.32 kcal mol−1by the KS-ELM, KS-HC-ELM, and KS-ACO-ELM methods and the artificial neural network (ANN) combined with KS-HC, respectively. This method predicts accurate values with much higher efficiency when compared to the larger basis set DFT calculation and may also achieve similarly accurate calculation results for larger molecules.

HOMOLYTIC C–H BOND DISSOCIATION ENERGIES OF HTPB BINDER NETWORK

2009 ◽  
Vol 08 (03) ◽  
pp. 519-528 ◽  
Author(s):  
SONGNIAN LI ◽  
LUOXIN WANG ◽  
YONG LIU ◽  
XINLIN TUO ◽  
XIAOGONG WANG
Keyword(s):  
Density Functional Theory ◽  
Structural Analysis ◽  
Density Functional ◽  
Bond Dissociation Energies ◽  
Functional Theory ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Tertiary Carbon ◽  
Carbon Radicals ◽  
Secondary Carbon

The C – H bond dissociation energies (BDEs) of hydroxyl-terminated polybutadiene (HTPB) binder have been computed using ab initio and density functional theory methods. Five different HTPB carbon radicals were produced by the ruptures of different C – H bonds. The structural analysis of radicals and the calculated BDEs showed that the studied C – H bonds could be divided into three groups. It was found that the weakest C – H bonds were those on the tertiary carbon atom linked to a vinyl function. The next were those on the secondary carbon attached to a vinyl function. The dissociation of these two kinds of C – H bonds determines the structure of the ultimate products during the aging of HTPB binder. The most stable C – H bonds were those in the methylene that were attached to the saturated carbon atoms.

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