Determination of the anharmonic potential constants for the ammonia molecule using an extended basis set of one-center wavefunctions

1975 ◽  
Vol 10 (1) ◽  
pp. 67-70
Author(s):  
L. V. Belyavskaya ◽  
G. O. Yarkovoi ◽  
V. E. Sorochinskaya ◽  
A. A. Stempkovskaya ◽  
V. P. Morozov
Keyword(s):  
Basis Set ◽  
Ammonia Molecule ◽  
Anharmonic Potential ◽  
Extended Basis

scholarly journals Determination of a Density Functional Tight Binding Model with an Extended Basis Set and Three-Body Repulsion for Carbon Under Extreme Pressures and Temperatures

2013 ◽  
Vol 117 (15) ◽  
pp. 7885-7894 ◽  
Author(s):  
Nir Goldman ◽  
Sriram Goverapet Srinivasan ◽  
Sebastien Hamel ◽  
Laurence E. Fried ◽  
Michael Gaus ◽  
...  
Keyword(s):  
Density Functional ◽  
Tight Binding ◽  
Basis Set ◽  
Tight Binding Model ◽  
Binding Model ◽  
Three Body ◽  
Extended Basis

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.

scholarly journals Unknown Knowns: Case Studies in Uncertainties in the Computation of Thermochemical Parameters

2020 ◽  
Author(s):  
John Simmie
Keyword(s):  
Heat Capacity ◽  
Gas Phase ◽  
Basis Set ◽  
Statistical Thermodynamic ◽  
Vibrational Modes ◽  
Heavy Atoms ◽  
New Methods ◽  
Formation Enthalpies ◽  
Thermochemical Parameters

<div>Both the computation of, and the uncertainties associated, with gas-phase molar formation enthalpies are now quite well established for systems comprised of tens of ‘heavy’ atoms chosen from the commonest elements. The same cannot be said for derived thermochemical quantities such as entropy, heat capacity and an enthalpy function. Whilst the application of well known statistical thermodynamic relations is mostly understood, the determination of the uncertainty with which such values can be obtained has been little studied — apart, that is, for a general protocol devised by Goldsmith et al. [J. Phys. Chem. A, 2012, 116, 9033–9057]. Specific examples from that work are explored here and it is shown that their estimates are overly pessimistic. It is also evident that for some species the calculated thermochemical parameters show very little variation with either the level of theory, or basis set, or treatment of vibrational modes — this renders the inclusion of such species in databases designed to validate new methods of limited value.<br></div>

The Br—O bond in halogen oxides — Empirical force constants and electronic characteristics

2004 ◽  
Vol 82 (6) ◽  
pp. 998-1005
Author(s):  
Rafael Escribano ◽  
Ismael K Ortega ◽  
Rafael G Mosteo ◽  
Pedro C Gómez
Keyword(s):  
Spectroscopic Data ◽  
Force Constants ◽  
Basis Set ◽  
Empirical Determination ◽  
Spectroscopic Information ◽  
Topological Characteristics ◽  
Different Characteristics ◽  
Halogen Oxides ◽  
Systematic Framework

A number of bromine oxides and mixed chlorine–bromine oxides for which spectroscopic information is available have been chosen to investigate the nature and characteristics of the Br—O bond. The study consists of the empirical determination of stretching force constants for these bonds from observed vibrational spectroscopic data and the analysis of the topological characteristics of the bonds via ab initio calculations. The latter have been performed at the MP2 level with a 6-311+G(2df) basis set, to provide a uniform and systematic framework for comparing these species. Three types of Br—O bonds have been found, with different characteristics of strength and electron density. The results are compared with those recently found for the Cl—O bond in chlorine oxides.Key words: bromine oxides, bond electronic structure.

Heats of formation for third-period hydrides: test of an extended basis set

1987 ◽  
Vol 91 (9) ◽  
pp. 2353-2354 ◽  
Author(s):  
Mark S. Gordon ◽  
John. Heitzinger
Keyword(s):  
Basis Set ◽  
Heats Of Formation ◽  
Extended Basis
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