Calculation of Magnetic Shielding and Susceptibility of H2O and FOH with Gauge Invariant Gaussian Basis Set

1976 ◽  
Vol 31 (12) ◽  
pp. 1727-1728 ◽  
Author(s):  
Matjaz Žaucer ◽  
Danilo Pumpernik ◽  
Milan Hladnik ◽  
Andrej Ažman
Keyword(s):  
Basis Set ◽  
Magnetic Shielding ◽  
Gauge Invariant ◽  
Finite Perturbation ◽  
Gaussian Basis Set ◽  
Experimental Values ◽  
Extended Basis

AbstractSusceptibility and magnetic shieldings of all nuclei are calculated for water and hypofluorous acid. A finite perturbation SCF method with gauge invariant gaussian basis set is used. Results calculated with a slightly extended basis set agree well with experimental values.

Finite Perturbation Studies of Magnetic Susceptibility and Shielding with GIAO

1977 ◽  
Vol 32 (5) ◽  
pp. 411-414 ◽  
Author(s):  
Matjaž Žaucer ◽  
Danilo Pumpernik ◽  
Milan Hladnik ◽  
Andrej Ažman
Keyword(s):  
Magnetic Susceptibility ◽  
Perturbation Method ◽  
Ab Initio ◽  
Basis Set ◽  
Magnetic Shielding ◽  
Gauge Invariant ◽  
Susceptibility Tensor ◽  
Atomic Orbitals ◽  
Magnetic Susceptibility Tensor ◽  
Finite Perturbation

Abstract The magnetic susceptibility tensor and proton and fluorine magnetic shielding tensors are cal­ culated for F2 and (FHF)- using an ab initio finite perturbation method with gauge-invariant atomic orbitals (GIAO). The discussion of the basis set deficiency shows that the calculated values for the susceptibilities are reliable. Simple additivity (Pascal rule) for the susceptibility is con­ firmed.

Basis set dependence of magnetic shielding constant calculated by the Hartree-Fock/finite perturbation method

1996 ◽  
Vol 203 (2) ◽  
pp. 159-175 ◽  
Author(s):  
Takuji Higashioji ◽  
Masahiko Hada ◽  
Manabu Sugimoto ◽  
Hiroshi Nakatsuji
Keyword(s):  
Perturbation Method ◽  
Basis Set ◽  
Magnetic Shielding ◽  
Hartree Fock ◽  
Finite Perturbation

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.

MP2 calculation of nuclear magnetic shielding constants involving gauge-invariant bases

1988 ◽  
Vol 66 (7) ◽  
pp. 1781-1785 ◽  
Author(s):  
Edouard C. Vauthier ◽  
Michel Comeau ◽  
Simone Odiot ◽  
Sandor Fliszar
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Spin Rotation ◽  
Basis Set ◽  
Magnetic Shielding ◽  
Resonance Spectroscopy ◽  
Correlation Effects ◽  
Gauge Invariant ◽  
Atomic Orbitals ◽  
Shielding Constants ◽  
Nuclear Magnetic

Dia- and paramagnetic shielding constants of HF, NH3, N2, H2O, and CO were calculated in the 4-31G, 4-31G*, and 6-31G** bases, using gauge-invariant atomic orbitals. Correlation effects were evaluated by 2nd-order perturbation theory: while the diamagnetic contributions are virtually unaffected by correlation, the paramagnetic parts (σρ) are modified by ~10 ppm in the 6-31G** basis. With or without correlation, calculated σρ values differ significantly from results obtained from measured spin-rotation constants. However, improvements in the basis set descriptions and inclusion of correlation yield chemical shift values for 15N and 17O converging toward their experimental counterparts obtained from conventional nuclear magnetic resonance spectroscopy.

DFT Benchmark Study of the O--O Bond Dissociation Energy in Peroxides Validated with High-Level Ab-Initio Calculations

2019 ◽  
Author(s):  
Danilo Carmona ◽  
Pablo Jaque ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Reference Value ◽  
Basis Set ◽  
Basis Sets ◽  
Mean Deviation ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
The Mean ◽  
Experimental Values ◽  
High Level ◽  
Almost All

<div><div><div><p>Peroxides play a central role in many chemical and biological pro- cesses such as the Fenton reaction. The relevance of these compounds lies in the low stability of the O–O bond which upon dissociation results in radical species able to initiate various chemical or biological processes. In this work, a set of 64 DFT functional-basis set combinations has been validated in terms of their capability to describe bond dissociation energies (BDE) for the O–O bond in a database of 14 ROOH peroxides for which experimental values ofBDE are available. Moreover, the electronic contributions to the BDE were obtained for four of the peroxides and the anion H2O2− at the CBS limit at CCSD(T) level with Dunning’s basis sets up to triple–ζ quality provid- ing a reference value for the hydrogen peroxide anion as a model. Almost all the functionals considered here yielded mean absolute deviations around 5.0 kcal mol−1. The smallest values were observed for the ωB97 family and the Minnesota M11 functional with a marked basis set dependence. Despite the mean deviation, order relations among BDE experimental values of peroxides were also considered. The ωB97 family was able to reproduce the relations correctly whereas other functionals presented a marked dependence on the chemical nature of the R group. Interestingly, M11 functional did not show a very good agreement with the established order despite its good performance in the mean error. The obtained results support the use of similar validation strategies for proper prediction of BDE or other molecular properties by DF Tmethods in subsequent related studies.</p></div></div></div>

Formulation of theLCAS MS SCF method within the Gaussian basis set

1980 ◽  
Vol 18 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Szczepan Roszak ◽  
Henryk Chojnacki
Keyword(s):  
Basis Set ◽  
Gaussian Basis Set

Net charges and valence AO's in the methylamines; the hydrogen basis set and the properties of nitrogen

1985 ◽  
Vol 63 (7) ◽  
pp. 1487-1491 ◽  
Author(s):  
Giuseppe Del Re ◽  
Sándor Fliszár ◽  
Michel Comeau ◽  
Claude Mijoule
Keyword(s):  
Basis Set ◽  
Basis Sets ◽  
Methyl Groups ◽  
Extended Form ◽  
Amine Nitrogen ◽  
Methyl Group ◽  
Net Charges ◽  
Extended Basis

Net charges and valence AO's for ammonia, methylamine, dimethylamine, and trimethylamine were calculated using extended basis sets. Superposition effects, evaluated by replacing Pople's standard 6-31G* basis by an extended form in which the basis of the ammonia H atoms and of the methyl groups of trimethylamine are retained in the treatment of each molecule, indicate that the quality of the treatment of amine nitrogen atoms is strongly dependent on the number of methyl groups. A new, augmented basis is proposed for the hydrogens, which appears to be reasonably well balanced: comparison with familiar (e.g., 6-31G*) calculations illustrates in what manner the treatment of nitrogen is worsened when even just one methyl group is replaced by hydrogen unless the impoverishment of the basis is suitably taken care of.

Highly accurate relativistic universal Gaussian basis set for Dirac-Fock-Breit calculations

2005 ◽  
Vol 102 (1) ◽  
pp. 1-7 ◽  
Author(s):  
L. G. M. De Macedo ◽  
R. C. Barbosa ◽  
A. B. F. da Silva
Keyword(s):  
Basis Set ◽  
Gaussian Basis Set
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