X-ray determination of effective charges on sulphur, phosphorus, silicon and chlorine atoms

Dolenko, G. N.

doi:10.1016/0022-2860(93)80253-r

Cited by 22 publications

(4 citation statements)

References 30 publications

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“…The simple potential model 1 corrected for relaxation effects for the carbon atom is given by where E C,1s is the carbon 1s core ionization energy, q A and q C are atomic charges, R AC is the internuclear distance between atoms A and C, and E relax is the relaxation energy for the ionization process. The first two terms in this equation can be derived from purely classical electrostatic considerations ,− or from quantum mechanical arguments. The k parameter can be identified as the average electrostatic interaction between an electron located in a core orbital near the nucleus of an atom and a valence shell of unit charge around this nucleus, or in quantum chemical terms, as the corresponding Coulomb integral.…”

Section: Relaxation Energymentioning

confidence: 99%

A Simple Potential Model Criterion for the Quality of Atomic Charges

et al. 1999

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The simple potential model has been shown to be useful in relating core electron binding energies measured in the X-ray region with mean dipole moment derivatives obtained from experimental infrared vibrational intensities. The importance of including relaxation corrections to the experimental 1s ionization energies of sp, sp 2 , and sp 3 hybridized carbon atoms are investigated here. Although relaxation energies obtained from 6-31G(d,p) and 6-311++G(3df,3p) basis sets using ∆SCF calculations show differences of about 1 eV for most molecules studied, relative differences are of the order of 0.1 eV. Exceptions are the CO, CO 2 , COS, and CS 2 molecules where discrepancies are larger. Relaxation energy corrections improve simple potential model fits with mean dipole moment derivatives for all carbon atom models but is most pronounced for the sp hybridized atoms. The simple potential model corrected for relaxation energies is investigated as a criterion for testing the quality of Mulliken, CHELPG, Bader and GAPT carbon atomic charges calculated from MP2/ 6-311++G(3d,3p) wave functions. The GAPT charges are in excellent agreement with the experimental mean dipole moment derivatives (within 0.067e) and provide superior statistical fits to the simple potential model when compared with those obtained for the other charges.

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Section: Relaxation Energymentioning

confidence: 99%

A Simple Potential Model Criterion for the Quality of Atomic Charges

et al. 1999

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“…The energy position of the core-to-core Kα emission feature has been known to shift with changes in sulfur bonding and oxidation state since at least 1936 when measured by Parratt using a double-crystal spectrometer . Additional measurements before the modern era of synchrotron capabilities were made infrequently, ,− but again indicated the sensitivity of the S Kα energy position to the S oxidation state. More recently, Alonso Mori et al measured S Kα XES using synchrotron radiation facilities and found good agreement between Kα energy shifts and valence electron configurations calculated using density functional theory (DFT) and ab initio multiple scattering based (FEFF) simulations .…”

Section: Introductionmentioning

confidence: 99%

Probing Sulfur Chemical and Electronic Structure with Experimental Observation and Quantitative Theoretical Prediction of Kα and Valence-to-Core Kβ X-ray Emission Spectroscopy

et al. 2020

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An extensive experimental and theoretical study of the Kα and Kβ high-resolution X-ray emission spectroscopy (XES) of sulfur-bearing systems is presented. This study encompasses a wide range of organic and inorganic compounds, including numerous experimental spectra from both prior published work and new measurements. Employing a linear-response time-dependent density functional theory (LR-TDDFT) approach, strong quantitative agreement is found in the calculation of energy shifts of the core-to-core Kα as well as the full range of spectral features in the valence-to-core Kβ spectrum. The ability to accurately calculate the sulfur Kα energy shift supports the use of sulfur Kα XES as a bulk-sensitive tool for assessing sulfur speciation. The fine structure of the sulfur Kβ spectrum, in conjunction with the theoretical results, is shown to be sensitive to the local electronic structure including effects of symmetry, ligand type and number, and, in the case of organosulfur compounds, to the nature of the bonded organic moiety. This agreement between theory and experiment, augmented by the potential for high-access XES measurements with the latest generation of laboratory-based spectrometers, demonstrates the possibility of broad analytical use of XES for sulfur and nearby third-row elements. The effective solution of the forward problem, i.e., successful prediction of detailed spectra from known molecular structure, also suggests future use of supervised machine learning approaches to experimental inference, as has seen recent interest for interpretation of X-ray absorption near-edge structure (XANES).

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“…Spectroscopic measurements are an important experimental source of atomic charge values. X-ray photoelectron spectroscopy (XPS), for example, yields a direct measure of the energy of internal core electrons, − and shifts in these energies provoked by changes in substituent atoms can be quantitatively related to atomic charges by a simple potential model. Relations between experimental core electron energies and calculated charges obtained from quantum chemical or empirical procedures have also been reported, for molecules such as the halomethanes, silanes, and germanes …”

Section: Introductionmentioning

confidence: 99%

Core Electron Energies, Infrared Intensities, and Atomic Charges

et al. 1997

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Carbon 1s electron binding energies determined by X-ray photoelectron spectroscopy and mean dipole moment derivatives obtained from experimental infrared intensities are shown to be related through the simple potential model proposed by Siegbahn and collaborators. The sp3 carbon atoms in 13 halomethanes, 2 ethanes, 3 methylacetylenes, cyclopropane, and ethylene oxide have 1s energies, which, after correction for electrostatic potentials from neighboring atoms, are linearly related to the carbon mean dipole moment derivatives, presenting a slope of 15.50 ± 0.29 eV/e. The sp2 carbons of ethylene, three haloethylenes, and three carbonyl compounds also exhibit a linear relationship having a significantly different slope of 17.37 ± 0.87 eV/e. The sp carbon atoms in acetylenes, cyanides, CO, CS2, CO2, and OCS show a third linear relationship, with a slope of 18.90 ± 0.75 eV/e. These slopes are proportional to the inverse atomic radii of sp3, sp2, and sp carbon atoms and according to the simple potential equation can be interpreted as estimates of Coulomb repulsion integrals involving these hybridized orbitals and the 1s core electron orbitals. Two basic assumptions of the potential model are investigated. The effect of relaxation energies on the 1s electron ionization processes is estimated as the difference between ΔSCF ionization energies and Koopmans' frozen orbital estimates obtained from 6-31G(d,p) wave functions. These results are compared with values obtained previously from the equivalent cores estimating procedure. Also the conceptual validity of identifying the carbon mean dipole moment derivatives as atomic charges is discussed within the framework of the charge−charge flux-overlap model.

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X-ray determination of effective charges on sulphur, phosphorus, silicon and chlorine atoms

Cited by 22 publications

References 30 publications

A Simple Potential Model Criterion for the Quality of Atomic Charges

A Simple Potential Model Criterion for the Quality of Atomic Charges

Probing Sulfur Chemical and Electronic Structure with Experimental Observation and Quantitative Theoretical Prediction of Kα and Valence-to-Core Kβ X-ray Emission Spectroscopy

Core Electron Energies, Infrared Intensities, and Atomic Charges

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