scholarly journals PSII manganese cluster: Protonation of W2, O5, O4 and His337 in the S1 state explored by combined quantum chemical and electrostatic energy computations

2014 ◽  
Vol 1837 (8) ◽  
pp. 1316-1321 ◽  
Author(s):  
Arturo Robertazzi ◽  
Artur Galstyan ◽  
Ernst Walter Knapp
Keyword(s):  
Quantum Chemical ◽  
Electrostatic Energy ◽  
Manganese Cluster

scholarly journals The Face-to-Face σ-Hole···σ-Hole Stacking Interactions: Structures, Energies, and Nature

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 877
Author(s):  
Yu Zhang ◽  
Weizhou Wang
Keyword(s):  
Quantum Chemical ◽  
Noncovalent Interactions ◽  
Electrostatic Energy ◽  
Stacking Interactions ◽  
Energy Component ◽  
Stacking Interaction ◽  
Face To Face ◽  
The Face ◽  
Π Stacking Interaction ◽  
Induction Energy

The existence of the π···π stacking interaction is well-known. Similarly, it is reasonable to assume the existence of the σ-hole···σ-hole stacking interaction. In this work, the structures, energies, and nature of the face-to-face σ-hole···σ-hole stacking interactions in the crystal structures have been investigated in detail by the quantum chemical calculations. The calculated results clearly show that the face-to-face σ-hole···σ-hole stacking interactions exist and have unique properties, although their strengths are not very significant. The energy component analysis reveals that, unlike many other dispersion-dominated noncovalent interactions in which the induction energies always play minor roles for their stabilities, for the face-to-face σ-hole···σ-hole stacking interaction the contribution of the induction energy to the total attractive energy is close to or even larger than that of the electrostatic energy. The structures, energies, and nature of the face-to-face σ-hole···σ-hole stacking interactions confined in small spaces have also been theoretically simulated. One of the important findings is that encapsulation of the complex bound by the face-to-face σ-hole···σ-hole stacking interaction can tune the electronic properties of the container.

scholarly journals Interaction of methanol with the oxygen-evolving complex: atomistic models, channel identification, species dependence, and mechanistic implications

2016 ◽  
Vol 7 (10) ◽  
pp. 6463-6476 ◽  
Author(s):  
Marius Retegan ◽  
Dimitrios A. Pantazis
Keyword(s):  
Photosystem Ii ◽  
Active Site ◽  
Quantum Chemical ◽  
Oxygen Evolving Complex ◽  
Manganese Cluster ◽  
Channel Identification ◽  
Atomistic Models ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Oxygen Evolving

Spectroscopy-oriented quantum chemical studies establish how methanol is delivered to the water-oxidizing active site of Photosystem II and how it interacts with the manganese cluster.

scholarly journals A Quantum Chemical Topology Picture of Intermolecular Electrostatic Interactions and Charge Penetration Energy

2021 ◽  
Author(s):  
Fernando Jiménez-Grávalos ◽  
Dimas Suárez
Keyword(s):  
Quantum Chemical ◽  
Electrostatic Interactions ◽  
Binding Energies ◽  
Electrostatic Energy ◽  
Total Binding Energy ◽  
Chemical Topology ◽  
Electrostatic Binding ◽  
Quantum Chemical Topology ◽  
Interacting Quantum Atoms ◽  
Definition Of

<div>Basing on the Interacting Quantum Atoms approach, we present herein a conceptual and theoretical framework of short-range electrostatic interactions, whose accurate description is still a challenging problem in molecular modeling. For all the non-covalent complexes in the S66 database, the fragment-based and atomic decomposition of the electrostatic binding energies is performed using both the charge density of the dimers and the unrelaxed densities of the monomers. This energy decomposition together with dispersion corrections gives rise to a pairwise approximation to the total binding energy. It also provides energetic descriptors at varying distance that directly address the atomic and molecular electrostatic interactions as described by point-charge or multipole-based potentials. Additionally, we propose a consistent definition of the charge penetration energy within quantum chemical topology, which is mainly characterized in terms of the intramolecular electrostatic energy. Finally, we discuss some practical implications of our results for the design and validation of electrostatic potentials.</div>

scholarly journals The Use of Quantum Chemical Semiempirical Methods to Calculate the Lattice Energies of Organic Molecular Crystals. Part I: The Three Polymorphs of Glycine

2000 ◽  
Vol 55 (6-7) ◽  
pp. 609-615 ◽  
Author(s):  
Gerhard Raabe
Keyword(s):  
Quantum Chemical ◽  
Chemical Method ◽  
Molecular Crystals ◽  
Lattice Energy ◽  
Potential Method ◽  
Electrostatic Energy ◽  
Semiempirical Methods ◽  
Quantum Chemical Method ◽  
Organic Molecular Crystals ◽  
Lattice Energies

Abstract A method to calculate the lattice energies of organic molecular crystals is described. It is based on the semiempirical quantum chemical MINDO/3 approximation but might also be used within the framework of any other quantum chemical method. The lattice energy is approximated by the sum of dispersion-, induction-, exchange repulsion-, and electrostatic energy. Different, however, from other schemes employed in this field, like for example the atom-atom-potential method, the variables in the expression for the lattice energy have not been fitted to reproduce experimental values and, therefore, the single contributions retain their original physical meaning. Moreover, the method offers the advantage that it may be directly applied to all compounds that can be treated within the framework of the underlying quantum chemical method. Thus, time consuming readjustment of the entire parameter set upon extension of the group of target molecules by another class of compounds becomes obsolete. As an example, the lattice energies of the three polymorphs of glycine are calculated.

scholarly journals The Use of Quantum-Chemical Semiempirical Methods to Calculate the Lattice Energies of Organic Molecular Crystals. Part II: The Lattice Energies of α- and β-Oxalic Acid (COOH)2

2002 ◽  
Vol 57 (12) ◽  
pp. 961-966 ◽  
Author(s):  
Gerhard Raabe
Keyword(s):  
Oxalic Acid ◽  
Quantum Chemical ◽  
Lattice Energy ◽  
Energy Difference ◽  
Electrostatic Energy ◽  
Semiempirical Methods ◽  
Stable Form ◽  
Crystal Lattices ◽  
Lattice Energies ◽  
Chemical Procedure

The lattice energies (ΔE lat) of α- and β-oxalic acid ((COOH)2) have been calculated using a recently introduced semiempirical quantum-chemical procedure. Within the framework of this method the lattice energy (ΔE lat) is evaluated as the sum of the semiempirically calculated intermolecular dispersion (ΔEdis), induction (ΔEind), repulsion (ΔErep), and electrostatic energy (ΔEels). The lattice energies of the two polymorphs of oxalic acid obtained in this way correlate not only with the results of other calculations but also with the experimentally determined heats of sublimation in that the α-modification, which has a somewhat higher heat of sublimation, is slightly more stable than the β-polymorph. However, additional quantum-chemical calculations at the non-empirical ab initio level (e. g. ZPE+MP2(FC)/6-311++G**//MP2(FC)/6-311++G**) revealed that the absolute values of the lattice energies and the heats of sublimation are not directly comparable to each other because the structures of the (COOH)2 molecules in the crystal lattices of both polymorphs differ significantly from that of the most stable form of the free molecule in the gasphase. At about 4.3 kcal/mol the calculated energy difference between the structure of the molecule in the solid state and the energetically most favourable conformation of the free (COOH)2 molecule in the gasphase is much smaller than that in the recently described case of α-glycine (28±2 kcal/mol). However, even such a small difference might be the source of serious problems if the heats of sublimation are employed to fit parameters to be used in the optimization of crystal packings.

scholarly journals A Quantum Chemical Topology Picture of Intermolecular Electrostatic Interactions and Charge Penetration Energy

2021 ◽  
Author(s):  
Fernando Jiménez-Grávalos ◽  
Dimas Suárez
Keyword(s):  
Quantum Chemical ◽  
Electrostatic Interactions ◽  
Binding Energies ◽  
Electrostatic Energy ◽  
Total Binding Energy ◽  
Chemical Topology ◽  
Electrostatic Binding ◽  
Quantum Chemical Topology ◽  
Interacting Quantum Atoms ◽  
Definition Of

<div>Basing on the Interacting Quantum Atoms approach, we present herein a conceptual and theoretical framework of short-range electrostatic interactions, whose accurate description is still a challenging problem in molecular modeling. For all the non-covalent complexes in the S66 database, the fragment-based and atomic decomposition of the electrostatic binding energies is performed using both the charge density of the dimers and the unrelaxed densities of the monomers. This energy decomposition together with dispersion corrections gives rise to a pairwise approximation to the total binding energy. It also provides energetic descriptors at varying distance that directly address the atomic and molecular electrostatic interactions as described by point-charge or multipole-based potentials. Additionally, we propose a consistent definition of the charge penetration energy within quantum chemical topology, which is mainly characterized in terms of the intramolecular electrostatic energy. Finally, we discuss some practical implications of our results for the design and validation of electrostatic potentials.</div>

Effect of energy filtering on micro-diffraction in the SEM

1994 ◽  
Vol 52 ◽  
pp. 604-605
Author(s):  
James F. Mancuso ◽  
Leo A. Fama ◽  
William B. Maxwell ◽  
Jerry L. Lehman ◽  
Hasso Weiland ◽  
...  
Keyword(s):  
Detection Efficiency ◽  
Ccd Camera ◽  
High Gain ◽  
Microchannel Plate ◽  
Electrostatic Energy ◽  
Energy Filtering ◽  
Electron Channelling ◽  
Low Energy Electrons ◽  
Low Sensitivity ◽  
Angular Field Of View

Micro-diffraction based crystallography is essential to the design and development of many classes of ‘crafted materials’. Although the scanning electron microscope can provide crystallographic information with high spatial resolution, its current utility is severely limited by the low sensitivity of existing diffraction techniques (ref: Dingley). Previously, Joy showed that energy filtering increased contrast and pattern visibility in electron channelling. This present paper discribes the effect of energy filtering on EBSP sensitivity and backscattered SEM imaging.The EBSP detector consisted of an electron energy filter, a microchannel plate detector, a phosphor screen, optical coupler, and a slow scan CCD camera. The electrostatic energy filter used in this experiment was constructed as a cone with 5 coaxial electrodes. The angular field-of-view of the filter was approximately 38°. The microchannel plate, which was the initial sensing component, had high gain and had 50% to 80% detection efficiency for the low energy electrons that passed through the retarding field filter.

ELECTROSTATIC ENERGY AND LATTICE VIBRATIONS IN THIN IONIC SLABS

1981 ◽  
Vol 42 (C6) ◽  
pp. C6-341-C6-343
Author(s):  
G. Kanellis ◽  
J. F. Morhange ◽  
M. Balkanski
Keyword(s):  
Electrostatic Energy ◽  
Lattice Vibrations
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