scholarly journals Paradigms and paradoxes: fractional electron charge

2021 ◽  
Author(s):  
Istvan Hargittai
Keyword(s):  
Nobel Prize ◽  
Atomic Charges ◽  
Partial Charge ◽  
Electron Charge ◽  
Solid Samples ◽  
Experimental Conditions ◽  
Generic Connection ◽  
Partial Atomic Charges

AbstractThere is hardly a generic connection between the partial atomic charges, a useful concept in chemistry, and the “fractionalization” of the electron accomplished under extreme experimental conditions in solid samples. Nonetheless, there is a relationship on a philosophical level. There is no information of who first introduced the concept of partial atomic charges in chemistry. In contrast, the physicists whose experiment turned the electron into excitations carrying a partial charge and whose theory provided the interpretation received the Nobel Prize for their discoveries.

scholarly journals The Charge State of Pt in Binary Compounds and Synthetic Minerals Determined by X-ray Absorption Spectroscopy and Quantum Chemical Calculations

Minerals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 79
Author(s):  
Polina V. Evstigneeva ◽  
Alexander L. Trigub ◽  
Dmitriy A. Chareev ◽  
Max S. Nickolsky ◽  
Boris R. Tagirov
Keyword(s):  
Intermetallic Compounds ◽  
Electron Density ◽  
Absorption Spectroscopy ◽  
Quantum Chemical ◽  
Electron Donors ◽  
Atomic Charges ◽  
Partial Charge ◽  
X Ray ◽  
Partial Atomic Charges ◽  
X Ray Absorption

The binary synthetic compounds of Pt with chalcogens (O, S, Se, Te), pnictogens (As, Sb, Bi), and intermetallic compounds with Ga, In, and Sn of various stoichiometry were studied via X-ray absorption spectroscopy (XAS). The partial atomic charges of Pt in the compounds were computed using quantum chemical density functional theory (DFT) based methods: the Bader (QTAIM) method, and the density-derived electrostatic and chemical (DDEC6) approach. Strong positive correlations were established between the calculated partial atomic charges of Pt and the electronegativity (χ) of ligands. The partial charge of Pt in PtL2 compounds increases much sharply when the ligand electronegativity increases than the Pt partial charge in PtL compounds. The effect of the ligand-to-Pt atomic ratio on the calculated Pt partial charge depended on ligand electronegativity. The DDEC6 charge of Pt increases sharply with the growth of the number of ligands in PtSn (n = 1, 2; electronegativity χ(S) >> χ(Pt)), weakly depends on the phase composition in PtTen (n = 1, 2; χ(Te) is slightly lower than χ(Pt)), and decreases (becomes more negative) with increase of the ligand-to-Pt ratio in intermetallic compounds with electron donors (χ(L) < χ(Pt), L = Ga, In, Sn). According to XANES spectroscopy, the number of 5d (L2,3 absorption edges) and 6p (L1-edge) electrons at the Pt site decreased when ligand electronegativity increased in chalcogenides and pnictides groups. An increase of the ligand-to-Pt ratio resulted in the increase of the Pt L3-edge white line intensity and area in all studied compounds. In the case of chalcogenides and pnictides, this behavior was consistent with the electronegativity rule as it indicated a loss of Pt 5d electrons caused by the increase of the number of ligands, i.e., acceptors of electrons. However, in the case of ligands–electron donors (Te, Sn, Ga, In) this observation is in apparent contradiction with the electronegativity arguments as it indicates the increase of the number of Pt 5d-shell vacancies (holes) with the increase of the number of the ligands, for which the opposite trend is expected. This behavior can be explained in the framework of the charge compensation model. The loss of the Pt d-electrons in compounds with low ligand electronegativity (χ(Pt) > χ(L)) was overcompensated by the gain of the hybridized s-p electron density, which was confirmed by Pt L1 - edge spectra analysis. As a result, the total electron density at the Pt site followed the electronegativity rule, i.e., it increased with the growth of the number of the ligands-electron donors. The empirical correlations between the Pt partial atomic charges and parameters of XANES spectral features were used to identify the state of Pt in pyrite, and can be applied to determine the state of Pt in other ore minerals.

scholarly journals Predicting partial atomic charges in siliceous zeolites

2019 ◽  
Vol 277 ◽  
pp. 184-196 ◽  
Author(s):  
Jarod J. Wolffis ◽  
Danny E.P. Vanpoucke ◽  
Amit Sharma ◽  
Keith V. Lawler ◽  
Paul M. Forster
Keyword(s):  
Atomic Charges ◽  
Partial Atomic Charges

scholarly journals Determining Partial Atomic Charges for Liquid Water: Assessing Electronic Structure and Charge Models

2020 ◽  
Author(s):  
Bowen Han ◽  
Christine Isborn ◽  
Liang Shi
Keyword(s):  
Electronic Structure ◽  
Dipole Moment ◽  
Charge Transfer ◽  
Liquid Water ◽  
Quantum Chemical ◽  
Water Dimer ◽  
Atomic Charges ◽  
Molecular Dipole ◽  
Molecular Dipole Moment ◽  
Partial Atomic Charges

Partial atomic charges provide an intuitive and efficient way to describe the charge distribution and the resulting intermolecular electrostatic interactions in liquid water. Many charge models exist and it is unclear which model provides the best assignment of partial atomic charges in response to the local molecular environment. In this work, we systematically scrutinize various electronic structure methods and charge models (Mulliken, Natural Population Analysis, CHelpG, RESP, Hirshfeld, Iterative Hirshfeld, and Bader) by evaluating their performance in predicting the dipole moments of isolated water, water clusters, and liquid water as well as charge transfer in the water dimer and liquid water. Although none of the seven charge models is capable of fully capturing the dipole moment increase from isolated water (1.85 D) to liquid water (about 2.9 D), the Iterative Hirshfeld method performs best for liquid water, reproducing its experimental average molecular dipole moment, yielding a reasonable amount of intermolecular charge transfer, and showing modest sensitivity to the local water environment. The performance of the charge model is dependent on the choice of the density functional and the quantum treatment of the environment. The computed molecular dipole moment of water generally increases with the percentage of the exact Hartree-Fock exchange in the functional, whereas the amount of charge transfer between molecules decreases. For liquid water, including two full solvation shells of surrounding water molecules (within about 5.5 A of the central water) in the quantum-chemical calculation converges the charges of the central water molecule. Our final pragmatic quantum-chemical charge assigning protocol for liquid water is the Iterative Hirshfeld method with M06-HF/aug-cc-pVDZ and a quantum region cutoff radius of 5.5 A.<br>

Cooperative Hydrogen-Bonding Effects in a Water Square:  A Single-Crystal Neutron and Partial Atomic Charges and Hardness Analysis Study

2005 ◽  
Vol 127 (31) ◽  
pp. 11063-11074 ◽  
Author(s):  
David R. Turner ◽  
Marc Henry ◽  
Clive Wilkinson ◽  
Garry J. McIntyre ◽  
Sax A. Mason ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Single Crystal ◽  
Atomic Charges ◽  
Analysis Study ◽  
Partial Atomic Charges ◽  
Cooperative Hydrogen Bonding

Partial atomic charges of amino acids in proteins

2004 ◽  
Vol 56 (1) ◽  
pp. 102-109 ◽  
Author(s):  
Annick Thomas ◽  
Alain Milon ◽  
Robert Brasseur
Keyword(s):  
Amino Acids ◽  
Atomic Charges ◽  
Partial Atomic Charges

scholarly journals Determining Partial Atomic Charges for Liquid Water: Assessing Electronic Structure and Charge Models

2020 ◽  
Author(s):  
Bowen Han ◽  
Christine Isborn ◽  
Liang Shi
Keyword(s):  
Electronic Structure ◽  
Dipole Moment ◽  
Charge Transfer ◽  
Liquid Water ◽  
Quantum Chemical ◽  
Water Dimer ◽  
Atomic Charges ◽  
Molecular Dipole ◽  
Molecular Dipole Moment ◽  
Partial Atomic Charges

Partial atomic charges provide an intuitive and efficient way to describe the charge distribution and the resulting intermolecular electrostatic interactions in liquid water. Many charge models exist and it is unclear which model provides the best assignment of partial atomic charges in response to the local molecular environment. In this work, we systematically scrutinize various electronic structure methods and charge models (Mulliken, Natural Population Analysis, CHelpG, RESP, Hirshfeld, Iterative Hirshfeld, and Bader) by evaluating their performance in predicting the dipole moments of isolated water, water clusters, and liquid water as well as charge transfer in the water dimer and liquid water. Although none of the seven charge models is capable of fully capturing the dipole moment increase from isolated water (1.85 D) to liquid water (about 2.9 D), the Iterative Hirshfeld method performs best for liquid water, reproducing its experimental average molecular dipole moment, yielding a reasonable amount of intermolecular charge transfer, and showing modest sensitivity to the local water environment. The performance of the charge model is dependent on the choice of the density functional and the quantum treatment of the environment. The computed molecular dipole moment of water generally increases with the percentage of the exact Hartree-Fock exchange in the functional, whereas the amount of charge transfer between molecules decreases. For liquid water, including two full solvation shells of surrounding water molecules (within about 5.5 A of the central water) in the quantum-chemical calculation converges the charges of the central water molecule. Our final pragmatic quantum-chemical charge assigning protocol for liquid water is the Iterative Hirshfeld method with M06-HF/aug-cc-pVDZ and a quantum region cutoff radius of 5.5 A.<br>

Sign in / Sign up

Export Citation Format

Share Document