Extended basis abinitio calculations on conformers of propanal

1985 ◽  
Vol 63 (4) ◽  
pp. 984-987 ◽  
Author(s):  
V. P. Gupta
Keyword(s):  
Dihedral Angle ◽  
Dipole Moments ◽  
Many Body ◽  
Gauche Conformer ◽  
Potential Barriers ◽  
Rotational Barriers ◽  
Extended Basis ◽  
Diagonal Harmonic ◽  
Optimized Geometries ◽  
Abinitio Calculations

Extended basis abinitio calculations on four conformations of propanal at the 4-31G and 6-31G** levels followed by many-body perturbative interaction calculations MP2 and MP3 have been conducted. Optimized geometries, heights of rotational barriers, dipole moments, ionisation potentials, and diagonal harmonic force constants have been reported. The s-cis conformer (dihedral angle CCCO = 0°) is found to be more stable than the gauche conformer (dihedral angle CCCO = 129.84°) by 5.07 kJ mol−1. Torisonal potential barriers s-cis/gauche, gauche/s-cis, and gauche/gauche have values 8.81, 3.74, and 1.84 kJ mol−1, respectively. It appears that meaningful values of rotational barriers can be obtained only after a careful optimization of the geometries of the conformations involved.

On excited states of the Au3 cluster: an ab initio study

Open Physics ◽  
2008 ◽  
Vol 6 (4) ◽  
Author(s):  
Alexander Rusakov ◽  
André Zaitsevskii
Keyword(s):  
Excited States ◽  
Spectroscopic Data ◽  
Reasonable Agreement ◽  
Dipole Moments ◽  
Electronic States ◽  
Ab Initio Study ◽  
Many Body ◽  
Transition Energies ◽  
Vertical Transition ◽  
Theoretical Results

AbstractExcited electronic states of the Au3 cluster are studied within the shape-consistent small-core relativistic pseudopotential model using many-body multipartitioning perturbation theory. Vertical transition energies and dipole moments are evaluated. For highly symmetric isomer, these theoretical results are in reasonable agreement with spectroscopic data from experiments.

scholarly journals Quantum many-body physics with ultracold polar molecules: Nanostructured potential barriers and interactions

2020 ◽  
Vol 102 (2) ◽  
Author(s):  
Andreas Kruckenhauser ◽  
Lukas M. Sieberer ◽  
Luigi De Marco ◽  
Jun-Ru Li ◽  
Kyle Matsuda ◽  
...  
Keyword(s):  
Polar Molecules ◽  
Many Body ◽  
Potential Barriers ◽  
Ultracold Polar Molecules ◽  
Many Body Physics

Transition Dipole Moments of n = 1, 2, and 3 Perovskite Quantum Wells from the Optical Stark Effect and Many-Body Perturbation Theory

2020 ◽  
Vol 11 (3) ◽  
pp. 716-723 ◽  
Author(s):  
Andrew H. Proppe ◽  
Grant W. Walters ◽  
Abdullah Y. Alsalloum ◽  
Ayan A. Zhumekenov ◽  
Edoardo Mosconi ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Quantum Wells ◽  
Stark Effect ◽  
Dipole Moments ◽  
Many Body ◽  
Transition Dipole ◽  
Transition Dipole Moments ◽  
Many Body Perturbation Theory ◽  
Optical Stark Effect

Dipole moments and conformation of α-disulphones. The gauche effect

1985 ◽  
Vol 50 (10) ◽  
pp. 2245-2251 ◽  
Author(s):  
Otto Exner ◽  
Václav Jehlička
Keyword(s):  
Dihedral Angle ◽  
Graphical Method ◽  
Benzene Solution ◽  
Dipole Moments ◽  
Statistical Treatment ◽  
X Ray ◽  
Gauche Effect

The dipole moments of substituted diphenyl disulphones I-III were measured in benzene solution and interpreted by the previously described graphical method. The results suggest an equilibrium of the ap and sc conformations in the ratio 3 : 1, at variance with various empirical rules and theories of the so-called gauche effect. A statistical treatment of X-ray data of various sulphonyl derivatives revealed essentially two preferred conformations: the more stable sc, with a broadened dihedral angle, and the less stable ap.

A many-body perturbation calculation of 4fN–4fN−15d electric dipole moments for lanthanide ions

2007 ◽  
Vol 439 (1-2) ◽  
pp. 363-366 ◽  
Author(s):  
Tao Chen ◽  
Chang-Kui Duan ◽  
Shangda Xia
Keyword(s):  
Electric Dipole ◽  
Dipole Moments ◽  
Lanthanide Ions ◽  
Perturbation Calculation ◽  
Many Body ◽  
Electric Dipole Moments

Ab initio molecular orbital study of simple 1,3-dipolar reactions

1976 ◽  
Vol 29 (3) ◽  
pp. 465 ◽  
Author(s):  
D Poppinger
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Transition States ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Molecular Orbital Study ◽  
Orbital Study ◽  
Extended Basis ◽  
Optimized Geometries

Ab initio molecular orbital calculations with minimal and extended basis sets have been carried out for the 1,3-dipolar addition of fulminic acid to acetylene, ethylene, ethynamine and propynenitrile. Optimized geometries are reported for the transition states HCNO+C2H2, HCNO+C2H4, HCNO+ C2HNH2, for the adducts isoxazole and 2-isoxazoline, and for nitrosocyclopropene as a possible intermediate. The calculations indicate that (a) these 1,3-dipolar reactions are synchronous processes, (b) the geometry of the transition state is insensitive to substitution and (c) of the isomeric substituted adducts, 5-aminoisoxazole and isoxazole-4-carbonitrile should be formed preferentially.

scholarly journals High-Resolution Mining of SARS-CoV-2 Main Protease Conformational Space: Supercomputer-Driven Unsupervised Adaptive Sampling

2021 ◽  
Author(s):  
Theo Jaffrelot Inizan ◽  
Frédéric Célerse ◽  
Olivier Adjoua ◽  
Dina El Ahdab ◽  
Luc-Henri Jolly ◽  
...  
Keyword(s):  
High Resolution ◽  
Adaptive Sampling ◽  
Dipole Moments ◽  
Sampling Strategy ◽  
Md Simulations ◽  
Conformational Space ◽  
Many Body ◽  
Main Protease ◽  
Comparison Results ◽  
Wide Range

We provide an unsupervised adaptive sampling strategy capable of producing microseconds-timescale molecular dynamics (MD) simulations of large biosystems using many-body polarizable force fields (PFF). The global exploration problem is decomposed into a set of separate MD trajectories that can be restarted within a selective process to achieve sufficient phase-space sampling. Accurate statistical properties can be obtained through reweighting. Within this highly parallel setup, the Tinker--HP package can be powered by an arbitrary large number of GPUs on supercomputers, reducing exploration time from years to days. This approach is used to tackle the urgent modeling problem of the SARS--CoV--2 Main Protease (Mpro) producing more than 38 microseconds of all-atom simulations of its apo, ligand-free, dimer using the high-resolution AMOEBA PFF. A first 15.14 microseconds simulation (physiological pH) is compared to available non--PFF long-timescale simulation data. A detailed clustering analysis exhibits striking differences between FFs, AMOEBA showing a richer conformational space. Focusing on key structural markers related to the oxyanion hole stability, we observe an asymmetry between protomers. One of them appears less structured resembling the experimentally inactive monomer for which a 6 microseconds simulation was performed as a basis of comparison. Results highlight the plasticity of Mpro active site. The C--terminal end of its less structured protomer is shown to oscillate between several states, being able to interact with the other protomer, potentially modulating its activity. Active and distal sites volumes are found to be larger in the most active protomer within our AMOEBA simulations compared to non-PFFs as additional cryptic pockets are uncovered. A second 17 microseconds AMOEBA simulation is performed with protonated His172 residues mimicking lower pH. Data show the protonation impact on the destructuring of the oxyanion loop. We finally analyze the solvation patterns around key histidine residues. The confined AMOEBA polarizable water molecules are able to explore a wide range of dipole moments, going beyond bulk values, leading to a water molecule counts consistent with experiment. Results suggest that the use of PFFs could be critical in drug discovery to accurately model the complexity of the molecular interactions structuring Mpro

Electrostatically embedded many-body method for dipole moments, partial atomic charges, and charge transfer

2012 ◽  
Vol 14 (21) ◽  
pp. 7669 ◽  
Author(s):  
Hannah R. Leverentz ◽  
Katie A. Maerzke ◽  
Samuel J. Keasler ◽  
J. Ilja Siepmann ◽  
Donald G. Truhlar
Keyword(s):  
Charge Transfer ◽  
Dipole Moments ◽  
Atomic Charges ◽  
Many Body ◽  
Partial Atomic Charges ◽  
Body Method

Molecular Level Interpretation of Vibrational Spectra of Ordered Ice Phases

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Peter J. Sharp ◽  
Francesco Paesani
Keyword(s):  
Normal Mode ◽  
Molecular Level ◽  
Dipole Moments ◽  
Normal Modes ◽  
Spectral Features ◽  
Many Body ◽  
Transition Dipole ◽  
Level Information ◽  
Normal Mode Calculations ◽  
Spectroscopic Signatures

<div> <div> <div> <p>We build on results from our previous investigation into ice Ih using a combination of classical many-body molecular dynamics (MB-MD) and normal mode (NM) calculations to obtain molecular level information on the spectroscopic signatures in the OH stretching region for all seven of the known ordered crystalline ice phases. The classical MB-MD spectra are shown to capture the important spectral features by comparing with experimental Raman spectra. This motivates the use of the classical simulations in understanding the spectral features of the various ordered ice phases in molecular terms. This is achieved through NM analysis to first demonstrate that the MB-MD spectra can be well recovered through the transition dipole moments and polarizability tensors calculated from each NM. From the normal mode calculations, measures of the amount of symmetric and antisymmetric stretching are calculated for each ice, as well as an approximation of how localized each mode is. These metrics aid in viewing the ice phases on a continuous spectrum determined by their density. As in ice Ih, it is found that most of the other ordered ice phases have highly delocalized modes and their spectral features cannot, in general, be described in terms of molecular normal modes. The lone exception is ice VIII, the densest crystalline ice phase. Despite being found only at high pressure, the symmetry index shows a clear separation of symmetric and antisymmetric stretching modes giving rise to two distinct features. </p> </div> </div> </div>

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