DENSITY FUNCTIONAL THEORY STUDY OF THE PHOTOELECTRON SPECTRA OF 5-METHYLTETRAZOLE

2013 ◽  
Vol 12 (01) ◽  
pp. 1250096 ◽  
Author(s):  
DELANO P. CHONG
Keyword(s):  
Density Functional ◽  
Slight Modification ◽  
Binding Energies ◽  
Photoelectron Spectra ◽  
Core Electron ◽  
Functional Theory ◽  
Electron Ionization Spectrum ◽  
Core Electrons ◽  
Vertical Ionization Energies ◽  
Electron Binding Energies

The molecule 5-methyltetrazole (5MTZ) can exist in two taumeric forms. The vertical ionization energies (VIEs) of both valence and core electrons of both the tautomers are calculated with our established DFT procedures and compared with available experimental data. For the 2H-tautomer, the average absolute deviations (AADs) for the outer-valence VIEs and core-electron binding energies (CEBEs) from experiment are below 0.1 eV, while the AAD for the inner-valence VIEs is much larger at 0.4 eV. For the 1H-tautomer, no observed valence VIEs have been reported and the AAD for the calculated CEBEs is 0.2 eV. The assignment of the experimental core-electron ionization spectrum is confirmed, but our results suggest a slight modification of the assignment of the UV photoelectron spectrum of the 2H-tautomer.

Density functional theory study of allopurinol

2013 ◽  
Vol 91 (7) ◽  
pp. 637-641 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Binding Energies ◽  
Dipole Polarizability ◽  
Equilibrium Geometry ◽  
Core Electron ◽  
Functional Theory ◽  
Valence Electrons ◽  
Vertical Ionization Energies ◽  
Electron Binding Energies

Allopurinol vapour is studied with density functional theory. Using the best method from past experience for each property, we predict the equilibrium geometry, vibrational spectrum, dipole moment, average dipole polarizability, UV absorption spectrum, vertical ionization energies of valence electrons, and core-electron binding energies.

Density-functional calculation of core-electron binding energies of glycine conformers

1996 ◽  
Vol 74 (6) ◽  
pp. 1005-1007 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Binding Energies ◽  
Basis Set ◽  
Stable Conformer ◽  
Absolute Deviation ◽  
Core Electron ◽  
Functional Theory ◽  
Electron Binding Energies ◽  
Electron Binding

Our recent procedure of computing accurate core-electron binding energies (CEBEs) with density-functional theory is applied to glycine conformers in this work. The procedure uses the unrestricted generalized transition-state model and a combined functional of Becke's 1988 exchange with Perdew's 1986 correlation. When a large basis set such as Dunning's correlation-consistent polarized valence quadruple zeta set is used, the average absolute deviation from experiment for the CEBEs of the most stable conformer of glycine is only 0.2 eV, compared with 18 eV for Koopmans' theorem. Key words: core-electron binding energies, density-functional theory, glycine.

Computational study of the structures and photoelectron spectra of 12 azabenzenes

2019 ◽  
Vol 97 (10) ◽  
pp. 697-703 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Computational Study ◽  
Binding Energies ◽  
Molecular Structures ◽  
Photoelectron Spectra ◽  
Basis Set ◽  
Integer Number ◽  
Core Electron ◽  
Core Electrons ◽  
Predicted Values ◽  
Vertical Ionization Energies

The molecular structures of 12 azabenzenes have been optimized with the Gaussian09 package at the level of coupled cluster singles and doubles with the basis set cc-pVTZ. The optimized geometry of each is used in the ADF13 program for the calculation of the vertical ionization energies of all the electrons. For both outer-shell and inner-shell valence electrons, the 2009 method of ΔPBE0(SAOP) is used, whereas the 1999 method of ΔPW86PW91 + Crel is employed for the core electrons. For degenerate orbitals, the alternative method chosen is to use localized orbitals, keeping the integer number of electrons, while giving up proper symmetry, rather than to keep symmetry with fractional electrons. The success of the computed results of valence ionization potentials of pyridine and the diazabenzenes gives confidence for the predicted values for the higher azabenzenes. The calculated results for core-electron binding energies provide incentive to experimentalists to measure them with X-ray photoelectron spectrometers and (or) synchrotron facilities.

Density functional theory study of the vertical ionization energies of the valence and core electrons of cyclopentadiene, pyrrole, furan, and thiophene

2011 ◽  
Vol 89 (12) ◽  
pp. 1477-1488 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Binding Energies ◽  
Test Cases ◽  
Absolute Deviation ◽  
Core Electron ◽  
Functional Theory ◽  
Ionization Energies ◽  
Benchmark Database ◽  
Vertical Ionization Energies

The procedure abbreviated as ΔPBE0(SAOP)/et-pVQZ, based on density functional theory, was developed recently for the calculation of vertical ionization energies of the valence electrons of organic and other small molecules and succeeded in giving results with an average absolute deviation of 0.21 eV from experiment for a collection of 115 reliable test cases of nonperhalo molecules. The objective of this work is to add a number of test cases to the benchmark database. We chose the set of molecules cyclo-C4H4X, with X = CH2, NH, O, and S, previously studied by many workers both experimentally and theoretically. The results show that the ΔPBE0(SAOP)/et-pVQZ procedure is not only as good as ab initio methods such as SAC-CI, OVGF, and ADC(3) in performance, but also handles inner valence ionized cations more efficiently. Although the core-electron binding energies of the titled molecules have not been as well investigated theoretically, we apply the methods we developed in recent years to calculate the binding energies of C1s, N1s, O1s, S1s, and S2p, which compare well with available experimental data.

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