Calculation Of Core-electron Binding Energies Research Articles

Density functional calculation of core-electron binding energies of isomers of C3H6O2 and C3H5NO

The core-electron binding energies of six isomers of C3H6O2 and four isomers of C3H5NO were calculated by a DFT/uGTS/scaled-pVTZ approach. An average absolute deviation from experiment of 0.15 eV was found for 14 C, N, and O 1s energies. The results confirm the distinctive nature of the X-ray photoelectron spectra (XPS) of isomers and support the use of electron spectroscopy complemented by accurate theoretical predictions as a tool for chemical analysis. © 1999 John Wiley & Sons, Inc. Int J Quant Chem 76: 44–50, 2000

Accurate density-functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set

Abstract Our efficient method of calculating accurate core-electron binding energies has been applied to many cases. In order to extend the application to larger systems, such as oligomers and clusters; model polymers; and adsorbates on metals, respectively, the use slightly smaller basis sets and geometry optimized by a semiempirical molecular orbital method such as Austin Model 1, without sacrificing accuracy should be aimed for. In this paper, we report the results of our study on the effects of using such poorer geometry and poorer basis sets.

Accurate density-functional calculation of core-electron binding energies by a total-energy difference approach

A procedure for calculating core-electron binding energies (CEBEs), based on a total-energy difference approach within Kohn–Sham density functional theory, was investigated. Ten functional combinations and several basis sets (including unscaled, scaled, and core-valence correlated functions) were studied using a database of reliable observed CEBEs. The functionals designed by Perdew and Wang (1986 exchange and 1991 correlation) were found to give the best performance with an average absolute deviation from experiment of 0.15 eV. The scaled basis sets did not perform satisfactorily, but it was found that the core-valence correlated cc-pCVTZ basis functions were an excellent alternative to the cc-pV5Z set as they provided equally accurate results and could be applied to larger molecules.

Accurate density-functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set. VI: Extension to boron-containing molecules.

Our procedure for calculating core-electron binding energies (CEBEs), based on the unrestricted generalized transition state model using B88/P86 functional, was extended to boron-containing molecules. Both unscaled (cc-pVTZ, cc-pVQZ, cc-pV5Z) and scaled (scaled-pVTZ and scaled-pVQZ) basis sets were used. The average absolute deviation from experiment for boron CEBEs with the scaled-pVTZ basis set was found to be 0.24 eV, compared to 0.23 eV for the much larger cc-pV5Z basis set.Keywords: DFT, boron, core-electron binding energies.

Accurate density-functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set. VI: Extension to boron-containing molecules.

Our procedure for calculating core-electron binding energies (CEBEs), based on the unrestricted generalized transition state model using B88/P86 functional, was extended to boron-containing molecules. Both unscaled (cc-pVTZ, cc-pVQZ, cc-pV5Z) and scaled (scaled-pVTZ and scaled-pVQZ) basis sets were used. The average absolute deviation from experiment for boron CEBEs with the scaled-pVTZ basis set was found to be 0.24 eV, compared to 0.23 eV for the much larger cc-pV5Z basis set.Keywords: DFT, boron, core-electron binding energies.

Accurate density functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set. IV. Application to isomers of C3H6O, C3H3NO, and C6H6

The unrestricted generalized transition-state model using a gradient-corrected density functional was shown in previous papers to be a reliable procedure for calculating core-electron binding energies. Relativistic corrections were estimated. Recently, a more efficient basis was proposed and tested. The results indicated that the new scaled polarized valence triple-zeta basis performs as well as the much larger cc-pV5Z basis set. This procedure is followed in the present study of the known isomers of C3H6O, C3H3NO, and C6H6. The results demonstrate that x-ray photoelectron spectroscopy, complemented by accurate theoretical calculations, can indeed be used to help chemical analysis.

Accurate density-functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set. (II). Confirmation with a total of seventy-six cases

Further calculations were performed to confirm that the scaling procedure in the calculation of core-electron binding energies proposed by Chong et al. [1] performs well for larger molecules. The procedure was tested on fifty-two new test cases including molecules involving elements from the third period such as SF 4 and ClF 3. In all cases the scaled pVTZ basis performs almost as well as the much larger cc-pV5Z. The average absolute deviation between the results from the scaled pVTZ and estimated complete basis set limit is 0.07 eV.

Accurate density-functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set. (III). Extension to open-shell molecules

Density functional theory and the unrestricted generalized transition state (uGTS) model were applied to study the core-electron binding energies (CEBEs) of open-shell molecules. Basis set scaling based on Clementi and Raimondi's rules for atomic screening was used along with the cc-pVTZ basis set. The scaled pVTZ basis set is almost as good as the cc-pV5Z and complete basis set limit in predicting CEBEs. For small molecules (O 2, NO, NF 2 and NO 2) the average absolute deviation (aad) of our prediction (scaled pVTZ) is only 0.29 eV. For the larger molecule (CF 3) 2NO the aad is 0.56 eV, compared with experimental uncertainty of 0.5 eV. Theoretical predicted multiplet splittings for the small molecules agree quite well with experiment: the average deviation is −0.33 eV. For (CF 3) 2NO the calculated multiplet splittings are much smaller than the experimental ones. We also predict the CEBEs of PO, SN and SO, which have not been observed experimentally.

Density functional calculations of core-electron binding energies of amines. Application to (CH 3) 3NNi and (CH 3) 4N +Ni

A procedure for computing accurate core-electron binding energies via density functional theory is applied to ten molecular systems containing amine and ammonium groups. The procedure uses the unrestricted generalized transition-state model. The method is used on model systems in which amine and ammonium groups interact with a hydroxide or chloride ion, as well as with a nickel atom. The results are used to shed some light on the interpretation of some characteristics of the XPS spectra of pre-electrolysed nickel surfaces used in electropolymerization reactions.

Density functional calculation of core-electron binding energies of transition metal carbonyl and nitrosyl complexes

Our recent procedure of the unrestricted generalized transition state (uGTS) model for density functional calculations of core-electron binding energies has been applied to seven carbonyl and nitrosyl inorganic complexes: Fe(CO) 5, Ni(CO) 4, Mn(CO) 4NO, Co(CO) 3NO, Fe(CO) 2(NO) 2, Mn(NO) 3CO and Cr(NO) 4. The exchange-correlation potential is based on a combined functional of Becke's exchange (B88) and Perdew's correlation (P86). The cc-pVTZ basis set was used for the calculation of neutral molecules, while for the partial cation created in the uGTS approach we scaled the cc-pVTZ basis set using a procedure based on Clementi and Raimondi's rules for atomic screening. The average absolute deviation of the calculated core-electron binding energy from experiment is 0.28 eV.

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

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.

Accurate density-functional calculation of core-electron binding energies with a scaled polarized triple-zeta basis set. Twelve test cases and application to three C 2H 4O 2 isomers

A scaling procedure based on Clementi and Raimondi's rules for atomic screening was proposed for atomic orbital basis sets in the unrestricted generalized transition state (uGTS) model of density functional calculation of core-electron binding energies (CEBEs). The exchange-correlation potential is based on a combined functional of Becke's exchange (B88) and Perdew's correlation (P86). This proposal was tested on CEBEs of twelve small molecules, including F 2, N 2 and H 2O, and applied to the computation of CEBEs of three isomers of C 2H 4O 2: acetic acid (CH 3COOH), methyl formate (HCOOCH 3), and glycolic aldehyde (CH 2OHCHO). In all cases, the new scaled pVTZ basis performs almost as well as the much larger cc-pV5Z and the average absolute difference between the results from the scaled pVTZ and estimated complete basis set limits is 0.04 eV.

Density-functional calculation of core-electron binding energies of C, N, O, and F

The unrestricted generalized transition-state model using B88/P86 functional with Dunning’s cc-pV5Z basis set, found to be an excellent method of calculating core-electron binding energies (CEBEs), was further applied to many more molecules, some of which contain atoms from the third period. Estimation of relativistic corrections has also been refined. The average absolute deviation of over 50 calculated CEBEs from experiment is 0.30 eV before inclusion of approximate relativistic corrections (Crel), and 0.23 eV after adding Crel. Those molecules with observed CEBEs served to confirm our procedure, whereas the other cases provided our prediction of CEBEs.

Accurate calculation of core-electron binding energies by the density-functional method

Using a basis set of atomic natural orbitals of valence triple-zeta plus double polarization quality, the core-electron binding energies (CEBEs) of HF, H 2O, N 2 and CO were computed by the deMon density-functional program with a combined functional of Becke's exchange (B88) with Perdew's correlation (P86). Of four different versions of the transition-state method tested, the unrestricted generalized transition-state (uGTS) model showed most promise. Two other functionals were tested but found to be inferior to the B88/P86 combination. The molecules HCN, CO 2 and H 2CO were added in the comparative study of basis set convergence. The best procedure found (the uGTS model using B88/P86 functional with Dunning's cc-pV5Z basis set) was applied to other molecules. The average deviation from experiment for 20 computed CEBEs is 0.23 eV.

Ab initio calculation of core-electron binding energies in small molecules

Vertical ionization potentials for core orbitals of HF, H 2O, CO, HCN, and H 2CO are calculated with an ab initio transition operator method, followed by Rayleigh-Schrödinger perturbation theory. The results are improved by using a transition atomic basis set. Relativistic corrections are estimated. The average absolute deviation of our final results from experiment is 0.4 eV for the eight cases studied.

Transition atomic basis set for the calculation of core-electron binding energies by a transition operator method

A transition atomic basis for calculating core-electron binding energies has been developed from studies of HF.H 2O and CO, and tested on H 2CO and HCN. The average error of such calculations with our new transition 6-31G basis is ≈1 eV.

Photoelectron spectra of single crystal diacetylene polymers

X-ray photoelectron spectra of two single crystal diacetylene polymers are reported. The observed and calculated core electron binding energies are in good agreement within the limits imposed by the experimental technique and the semi-empirical calculations employed. UV photoelectron spectra can, in principle, provide information about the valence bands of the conjugated polymer chain but overlapping sidegroup bands prevented this for the materials investigated.