scholarly journals Ab Initio Study of Geminal Steric Hindrance Effects on the Stability of Conformations of Cyclohexane Derivatives

2005 ◽  
Vol 2005 (8) ◽  
pp. 508-515 ◽  
Author(s):  
Davood Nori-Shargh ◽  
Mostafa Mohamadpour Amini ◽  
Maryam Jafari ◽  
Farzad Deyhimi ◽  
Saeed Jameh-Bozorghi
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Energy Barrier ◽  
Density Functional ◽  
Energy Difference ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Conformational Properties ◽  
The Stability ◽  
Twist Boat

Ab initio and density functional theory methods (HF/3-21G*//HF/3-21G*, MP2/3-21G*//HF/3-21G*, B3LYP/3-21G*//HF/3-21G*, B3LYP/LANL2DZ*//HF/LANL2DZ*, MP2/LANL2DZ*//HF/LANL2DZ* and HF/LANL2DZ*//HF/LANL2DZ*) used to investigate the conformational properties of cyclohexane, 1,1-dimethylcyclohexane, 1,1-di-tert-butylcyclohexane, 1,1-bis(trimethylsilanyl)cyclohexane, 1,1-bis(trimethylgermanyl)cyclohexane and 1,1-bis(trimethylstannyl)cyclohex ane showed that the energy difference between the chair and twist-boat conformations and also the ring flipping energy barrier decreases from cyclohexane, 1,1-dimethylcyclohexane to 1,1-di-tert-butylcyclohexane, and increases from 1,1-bis(trimethylsilanyl)cyclohexane, 1,1-bis(trimethylgermanyl)cyclohexane to 1,1-bis(trimethylstannyl)cyclohexane.

Ab Initio Study of Conformational Properties of (Z,Z,Z)-Cyclonona-1,3,6-Triene

2003 ◽  
Vol 2003 (9) ◽  
pp. 546-548
Author(s):  
Davood Nori-Shargh ◽  
Mostafa Mohammadpour Amini ◽  
Saeed Jameh-Bozorghi ◽  
Nooshin Heydari laalee
Keyword(s):  
Ab Initio ◽  
Energy Barrier ◽  
Density Functional ◽  
Stable Form ◽  
Ab Initio Study ◽  
Ring Inversion ◽  
Functional Theory ◽  
Conformational Properties ◽  
Twist Boat ◽  
Calculated Energy Barrier

Ab initio molecular orbital and density functional theory (DFT) calculations, applied to ( Z,Z,Z)-cyclonona-1,3,6-triene (1) have revealed that the calculated energy barrier for ring inversion of the twist-boat ( C1 symmetry) conformation of 1 as a most stable form is 8.41 kcal mol−1, as calculated by the MP2/6-31G*//HF/6-31G* method

Ab initio Study of Configurational and Conformational Properties of Cyclodeca-1,2,4,6,7,9-Hexaene and Cyclodeca-1,2,4,6,8,9-Hexaene†

2003 ◽  
Vol 2003 (7) ◽  
pp. 384-385 ◽  
Author(s):  
Davood Nori-Shargh ◽  
Nasrin Sarogh-Farahani ◽  
Saeed Jameh-Bozorghi ◽  
Farzad Deyhimi ◽  
Mohammad-Reza Talei Bavil Olyai ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Density Functional ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Conformational Properties

Ab initio molecular orbital and density functional theory (DFT) calculations, used to calculate the structure optimisation and configurational features of cyclodeca-1,2,4,6,7,9-hexaene (1) and cyclodeca-1,2,4,6,8,9-hexaene (2), showed that the important structures in compound 1 are: RZRZ ( D2 symmetry), RZSZ ( C2h symmetry) and for compound 2 are: RSZZ ( C1 symmetry), RRZZ ( C2 symmetry).

Effect of Substitution for Insertion of CO2 into Epoxides and Aziridines: An Ab Initio Study

2020 ◽  
Vol 73 (1) ◽  
pp. 30
Author(s):  
Yunhan Yang ◽  
Fenji Li ◽  
Cuicui Yang ◽  
Lijuan Jia ◽  
Lijuan Yang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Free Energy ◽  
Reaction Mechanism ◽  
Ab Initio ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Concerted Mechanism

The insertion of CO2 into epoxides and aziridines has been studied using density functional theory (B3LYP) and ab initio (MP2) methods, and the effect of substitution for the two reactions are further explored. It is found that the reactivity of epoxides and aziridines are similar, and insertion of CO2 proceeds through a concerted mechanism. The substitutions of methyl and phenyl does not change the reaction mechanism, but the transition state for the substitution on the attacking position becomes loose with a lower free energy barrier. The substitutions of methyl and phenyl decrease the free energy barrier, with phenyl substitution having a greater affect. The results also show that the free energy barriers for the insertions of CO2 into aziridines are ~10kcalmol−1 lower than the corresponding reactions of CO2 with epoxides.

scholarly journals STRUCTURAL AND ELECTRONIC PROPERTIES OF BRIDGED BITHIOPHENE S-OXIDES (BTO) WITH S, S=O, O, SiH2 and BH2 BRIDGE: SEMI-EMPIRICAL AND AB INITIO STUDY

2010 ◽  
Vol 18 (18) ◽  
pp. 1-10
Author(s):  
Banjo Semire ◽  
Isaiah Ajibade Adejoro ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Empirical Methods ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Semi Empirical ◽  
Good Agreement

In this paper, we theoretically studied the geometries, stabilities, electronic and thermodynamic properties of bridged bithiophene S-oxide (BTO-X) derivates (with X = BH2, SiH2, S, S=O, and O) by using semi-empirical methods, ab-initio, and Density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with that of B3LYP/6-31G(d). The bandgap calculated by B3LYP/6-31G(d) ranged from 3.94eV (BTO-O)-3.16eV (BTO-BH2). The absorption λmax calculated suing B3LYP/6-31G(d) shifted to longer wavelength with X=BH2, SiH2, and S=O due to enhancement of π-conjugated system whereas, BTO-S and BTO-O shifted to shorter wavelengths as compared to dimmer thiophene S-oxide (2TO).

scholarly journals Ab initio study of elastic anisotropies and thermal conductivities of rhenium diborides in different crystal structures

RSC Advances ◽  
2020 ◽  
Vol 10 (61) ◽  
pp. 37142-37152
Author(s):  
Yi X. Wang ◽  
Ying Y. Liu ◽  
Zheng X. Yan ◽  
W. Liu ◽  
Jian B. Gu
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Crystal Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Ab Initio Study ◽  
Ambient Conditions ◽  
Functional Theory ◽  
Thermal Conductivities

The phase stabilities, elastic anisotropies, and thermal conductivities of ReB2 diborides under ambient conditions have been investigated by using density functional theory calculations.

Optical and dielectric properties of lead perovskite and iodoplumbate complexes: an ab initio study

2020 ◽  
Vol 22 (33) ◽  
pp. 18423-18434
Author(s):  
Malladi Srikanth ◽  
Mailde S. Ozório ◽  
Juarez L. F. Da Silva
Keyword(s):  
Density Functional Theory ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Optical Dielectric Constant ◽  
Energetic Stability ◽  
Optical Dielectric

Optical and dielectric properties, and energetic stability orders of black phase of perovskites and yellow phase of iodoplumbates have been studied using density functional theory; where the optical dielectric constant varies with the polymorphic phase and nature of cation.

AB INITIO STUDY OF STRUCTURAL STABILITY AND MAGNETIC PROPERTIES OF Con(n = 2 - 10): A STUDY BASED ON PSEUDOPOTENTIALS DFT

2011 ◽  
Vol 22 (04) ◽  
pp. 359-369
Author(s):  
M. SAMAH ◽  
B. MOULA
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Ground State ◽  
Density Functional ◽  
Magnetic Moments ◽  
Stability Study ◽  
Ab Initio Study ◽  
Functional Theory ◽  
The Stability ◽  
Magic Cluster

The lowest-energy geometric and isomers of freestanding Co n clusters (n = 2 - 10) and their corresponding magnetic moments have been studied using the Siesta code based on pseudopotential density-functional theory. The calculated results show that there are many isomers near the ground state. Different isomers hold different magnetic moment. The stability study shows that among the investigated clusters, the hexamer one is the most stable and is the magic cluster. Dissociation channels energy are also studied.

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