Modelling Electrostatic Potential from Experimentally Determined Charge Densities. II. Total Potential

Using the carrier-ion complex valinomycin-K+, current/voltage (I/U ) characteristics were registered for planar asymmetric lipid bilayers composed on one side of a phospholipid mixture and on the other side of rough mutant lipopolysaccharide. This system resembles the lipid matrix of the outer membrane of Gram-negative bacteria. The evaluation of the current/voltage curves yielded a highly asymmetric electrical potential barrier. The total potential difference between the phospholipid and the lipopolysaccharide was -85 mV, a result which cannot be explained by contributions of Gouy-Chapman potentials alone. The possible contribution of dipole potentials and influences of headgroup effects are discussed. It is shown that the asymmetry of the I/U-characteristic results from the differences of the surface charge densities of the two monolayers but not from those of the states of order of their hydrocarbon chains.

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Electrostatic potential in crystals of α-boron, γ-boron and boron carbide

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2018-2080 ◽

2018 ◽

Vol 233 (9-10) ◽

pp. 663-673

Author(s):

Christian B. Hübschle ◽

Sander van Smaalen

Keyword(s):

Boron Carbide ◽

Electrostatic Potential ◽

Chemical Bonds ◽

Charge Densities ◽

Icosahedral Cluster ◽

Hirshfeld Surfaces ◽

Infinite Network ◽

Dynamic Charge ◽

Extended Solids ◽

Bonding Characteristics

Abstract An overview is given of the recently proposed method for computation of the electrostatic potential (ESP) of dynamic charge densities derived from multipole models [C. B. Hubschle, S. van Smaalen, J. Appl. Crystallogr. 2017, 50, 1627]. The dynamic ESP is presented for the multipole models of the boron polymorphs α-B12 and γ-B28, and stoichiometric boron carbide B13C2. Minimum values of the ESP are conspiciously equal at approximately −1 electron/Å. Regions with the ESP close to its minimum value form an extended network throughout the crystal structures at locations far away from atoms and bonds. Boron and boron carbide are extended solids containing an infinite network of strong chemical bonds. We have shown that for such solids, the ESP can usefully considered on Hirshfeld surfaces encompassing groups of atoms. Accordingly, we discuss bonding in boron and boron carbide with aid of the ESP on the Hirsfeld surface encompassing a B12 icosahedral cluster. The structure of the ESP corroborates the interpretation of the bonding characteristics previously proposed for α-B12, γ-B28 and B13C2.

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The electrostatic potential of dynamic charge densities

Journal of Applied Crystallography ◽

10.1107/s1600576717013802 ◽

2017 ◽

Vol 50 (6) ◽

pp. 1627-1636 ◽

Cited By ~ 4

Author(s):

Christian B. Hübschle ◽

Sander van Smaalen

Keyword(s):

Charge Density ◽

Maximum Entropy ◽

Single Molecule ◽

Electrostatic Potential ◽

Zero Point ◽

Summation Method ◽

Molecular Surface ◽

Total Charge ◽

Charge Densities ◽

Dynamic Charge

A procedure to derive the electrostatic potential (ESP) for dynamic charge densities obtained from structure models or maximum-entropy densities is introduced. The ESP essentially is obtained by inverse Fourier transform of the dynamic structure factors of the total charge density corresponding to the independent atom model, the multipole model or maximum-entropy densities, employing dedicated software that will be part of theBayMEMsoftware package. Our approach is also discussed with respect to the Ewald summation method. It is argued that a meaningful ESP can only be obtained if identical thermal smearing is applied to the nuclear (positive) and electronic (negative) parts of the dynamic charge densities. The method is applied to structure models of DL-serine at three different temperatures of 20, 100 and 298 K. The ESP at locations near the atomic nuclei exhibits a drastic reduction with increasing temperature, the largest difference between the ESP from the static charge density and the ESP of the dynamic charge density being atT= 20 K. These features demonstrate that zero-point vibrations are sufficient for changing the spiky nature of the ESP at the nuclei into finite values. On 0.5 e Å−3isosurfaces of the electron densities (taken as the molecular surface relevant to intermolecular interactions), the dynamic ESP is surprisingly similar at all temperatures, while the static ESP of a single molecule has a slightly larger range and is shifted towards positive potential values.

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Electrostatic potential of dynamic charge densities

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273316098727 ◽

2016 ◽

Vol 72 (a1) ◽

pp. s86-s86

Author(s):

Christian B. Hübschle ◽

Sander van Smaalen

Keyword(s):

Electrostatic Potential ◽

Charge Densities ◽

Dynamic Charge

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Calculation of electrostatic potentials from multipole charge densities

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1524/zkri.1993.208.part-2.167 ◽

1993 ◽

Vol 208 (2) ◽

Author(s):

Hendrik L. De Bondt ◽

N. M. Blaton ◽

O. M. Peeters ◽

C. J. De Ranter

Keyword(s):

High Resolution ◽

Single Crystal ◽

Charge Density ◽

Electrostatic Potential ◽

Electron Distribution ◽

Density Model ◽

Slater Type ◽

Single Crystal Diffraction ◽

Charge Densities ◽

Resolution Single

AbstractA rigorous analytical expression is derived for the electrostatic potential originating from aspherical atomic multipole electron densities according to the Stewart or Hansen-Coppens charge density model with a Slater type radial electron distribution. Such models are widely used to determine charge distributions from high resolution single crystal diffraction experiments.

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