Ab initio molecular orbital calculations of the internal rotational potential of biphenyl using polarized basis sets with electron correlation correction

1991 ◽  
Vol 95 (1) ◽  
pp. 139-144 ◽  
Author(s):  
Seiji Tsuzuki ◽  
Kazutoshi Tanabe
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Electron Correlation ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Polarized Basis Sets ◽  
Correlation Correction

Structures of simple anions from ab initio molecular orbital calculations

1976 ◽  
Vol 29 (8) ◽  
pp. 1635 ◽  
Author(s):  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Basis Set ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Limited Information ◽  
Orbital Theory ◽  
Comparable Quality ◽  
Split Valence ◽  
Theoretical Results

Ab initio molecular orbital theory with the minimal STO-3G and split-valence 4-31G basis sets is used to obtain geometries of 18 anions:OH-, NH2-, HF2-, BH4-, BF4-, C22-, CN-, NCN2-, N3-, NO2-, NO3-, 0CCO2-, CO32-, HCOO-, CH3COO-, C2O42-, C4O42- and C(CN)3-. The theoretical results are compared with experimental results from the literature. The STO-3G basis set performs somewhat worse for anions than for neutral molecules. On the other hand, the 4-31G basis set gives good results and predicts bond lengths to within 0.02� for all the molecules considered. Limited information on bond angle predictions suggests that these are of comparable quality to those for neutral molecules. The tricyanomethanide ion is predicted to be planar.

Ab initio molecular orbital study of simple 1,3-dipolar reactions

1976 ◽  
Vol 29 (3) ◽  
pp. 465 ◽  
Author(s):  
D Poppinger
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Transition States ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Molecular Orbital Study ◽  
Orbital Study ◽  
Extended Basis ◽  
Optimized Geometries

Ab initio molecular orbital calculations with minimal and extended basis sets have been carried out for the 1,3-dipolar addition of fulminic acid to acetylene, ethylene, ethynamine and propynenitrile. Optimized geometries are reported for the transition states HCNO+C2H2, HCNO+C2H4, HCNO+ C2HNH2, for the adducts isoxazole and 2-isoxazoline, and for nitrosocyclopropene as a possible intermediate. The calculations indicate that (a) these 1,3-dipolar reactions are synchronous processes, (b) the geometry of the transition state is insensitive to substitution and (c) of the isomeric substituted adducts, 5-aminoisoxazole and isoxazole-4-carbonitrile should be formed preferentially.

Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations

2000 ◽  
Vol 55 (1-2) ◽  
pp. 315-322
Author(s):  
Nobuo Nakamura ◽  
Hirotsugo Masui ◽  
Takahiro Ueda
Keyword(s):  
Hydrogen Bond ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Quadrupole Interaction ◽  
Bond Distance ◽  
Nuclear Quadrupole Interaction ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Imidazole Derivatives ◽  
Nuclear Quadrupole

Ab initio Hartree-Fock molecular orbital calculations were applied to the crystalline imidazole and its derivatives in order to examine systematically the effect of possible N-H---N type hydrogen bond-ing on the nuclear quadrupole interaction parameters in these materials. The nitrogen quadrupole coupling constant (QCC) and the asymmetry parameter (η) of the electric field gradient (EFG) were found to depend strongly on the size of the molecular clusters, from single molecule, to dimer, trimer and to the infinite molecular chain, i.e., crystalline state, implying that the intermolecular N-H -N hydrogen bond affects significantly the electronic structure of imidazole molecule. A certain correla-tion between the QCC of 14N and the N-H bond distance R was also found and interpreted on the basis of the molecular orbital theory. However, we found that the value of the calculated EFG at the hy-drogen position of the N-H group, or the corresponding QCC value of 2 H, increases drastically as R-3 when R is shorter than about 0.1 nm, due probably to the inapplicability of the Gaussian basis sets to the very short chemical bond as revealed in the actual imidazole derivatives. We suggested that the ob-served N-H distances in imidazole derivatives should be re-examined.

Nitrosyl cyanide and related aspects of the ONCN potential surface

1978 ◽  
Vol 31 (11) ◽  
pp. 2349 ◽  
Author(s):  
BG Gowenlock ◽  
L Radom
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Related Species ◽  
Potential Surface ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Hartree Fock ◽  
Split Valence ◽  
Good Agreement

Ab initio molecular orbital calculations using the restricted Hartree-Fock approach have been carried out for nitrosyl cyanide and related species on the ONCN potential surface. Full geometry optimizations have been performed with the minimal STO-3G and split-valence 4-31G basis sets. Calculated (4-31G) geometries are in good agreement with available experimental data as are the energy changes in the reactions ONCN → NO + CN and NO + CN → N2 + CO. Possible mechanisms are discussed.

Ab Initio Studies on the Interaction Between Copper(I) and 5-Nitrotetrazolate Anion

2017 ◽  
Vol 68 (1) ◽  
pp. 12
Author(s):  
V. Venkatesan
Keyword(s):  
Binding Energy ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Natural Bond Orbital ◽  
Energy Difference ◽  
Atoms In Molecules ◽  
Basis Sets ◽  
Molecular Orbital Calculations

<p class="p1">Ab initio molecular orbital calculations on the interaction between Copper(I) and 5-nitrotetrazolate anion were done using different basis sets, at the HF, B3LYP and MP2 levels of theory. Three minima were found to 1A, 1B and IC structures of Cu(I)-5-NTz complex. At the B3LYP/LanL2DZ level, the energy difference between 1A and 1B was computed to be 8.18 kcal/mol, while that between 1A and 1C is 22.76 kcal/mol. The presence of both Cu-N and Cu-O interactions is revealed in 1A structure using both natural bond orbital and atoms-in-molecules analyses, which makes more stable than those of 1B and 1C complexes. The binding energy corrected for both ZPE and BSSE for 1A is found to be -150.59 kcal/mol at the B3LYP/LanL2DZ level. The barrier for the 1B <span class="s1">→</span> 1A and 1C <span class="s1">→</span> 1B conversion is calculated to be 7.80 kcal/mol and 9.40 kcal/mol, respectively.</p>

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