The Molecular and Electronic Structure of Tetrasulphur-dinitride; a Study by ab initio Molecular Orbital Methods and Photoelectron Spectroscopy

1982 ◽  
Vol 37 (9) ◽  
pp. 1061-1067 ◽  
Author(s):  
Michael H. Palmer ◽  
Woon Ming Lau ◽  
Nicholas P. C. Westwood
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Koopmans Theorem ◽  
Double Zeta ◽  
Reasonable Prediction ◽  
Excitation Processes ◽  
Molecular And Electronic Structure

Abstract The He (I) photoelectron spectrum of gaseous S4N2 is reported, and an assignment is made on the basis of the correlation with ab initio molecular orbital calculations. The latter, based upon the recently optimised geometry of Cѕ symmetry, used both a large basis set of greater than double zeta quality, together with configuration for both the ground state and the ionised states. The Koopmans’ Theorem order gives a reasonable prediction of the order of states for most of the low energy ionised states; beyond IP5 additional states involving excitation processes in conjunction with ionisation were computed. The numerical agreement between the observed IP’s and the CI value is reasonable.

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

1981 ◽  
Vol 36 (11) ◽  
pp. 1246-1252 ◽  
Author(s):  
Michael H. Palmer ◽  
Isobel Simpson ◽  
J. Ross Wheeler
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Relative Stability ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Molecular Orbital Calculations ◽  
Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

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.

Molecular Orbital Calculations of Cu-Halides

1981 ◽  
Vol 36 (10) ◽  
pp. 1095-1099 ◽  
Author(s):  
H. Itoh
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Energy Levels ◽  
Basis Set ◽  
Orbital Energy ◽  
Ionic Character ◽  
Molecular Orbital Calculations ◽  
Ab Initio Hf ◽  
Mo Theory

An ab initio HF MO theory is applied to CuX, CuX2 (X = F and Cl) and (CuCl)3 . Although the detailed sequence of energy levels depends upon the basis set used, high-lying orbital energy levels have largely halogen p-like character, whereas low-lying orbital energy levels have largely Cu 3 d-like character. This is in agreement with the chemical intuition of a highly ionic character of these compounds.

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