A-site ordering in colossal magnetoresistance manganite La[sub 1−x]Sr[sub x]MnO[sub 3]? Molecular dynamics simulations and quantum mechanics calculations

2009 ◽  
Vol 131 (9) ◽  
pp. 094503 ◽  
Author(s):  
Yun Hee Jang ◽  
François Gervais ◽  
Yves Lansac
Keyword(s):  
Molecular Dynamics ◽  
Quantum Mechanics ◽  
Molecular Dynamics Simulations ◽  
Colossal Magnetoresistance ◽  
Dynamics Simulations ◽  
A Site

UNDERSTANDING DIFFERENT LCST LEVELS OF POLY(N-ALKYLACRYLAMIDE)S BY MOLECULAR DYNAMICS SIMULATIONS AND QUANTUM MECHANICS CALCULATIONS

2011 ◽  
Vol 10 (03) ◽  
pp. 359-370 ◽  
Author(s):  
JUAN PANG ◽  
HU YANG ◽  
JING MA ◽  
RONGSHI CHENG
Keyword(s):  
Molecular Dynamics ◽  
Quantum Mechanics ◽  
Aqueous Solutions ◽  
Molecular Dynamics Simulations ◽  
Steric Effect ◽  
Conformational Transition ◽  
Methyl Group ◽  
Branched Chain ◽  
Dynamics Simulations ◽  
Different Levels

Poly(N-alkylacrylamide) is a group of thermo-sensitive polymers that include poly (N-isopropylacrylamide), poly(N-n-propylacrylamide), poly(N-isopropylmethacryl-amide), and so on. The polymers exhibit different levels of lower critical solution temperatures (LCST) in aqueous solutions. In this article, their monomers and oligomers with 10 repeating units are selected, respectively, to demonstrate the cause of different LCST levels of the polymers in aqueous solutions using molecular dynamics simulations and quantum mechanics calculations. The monomers have functional groups of different steric volume that greatly affect the conformational transition of chains and LCST levels of the polymers. A branched chain of N-propyl group in N-isopropylacrylamide and an additional methyl group at α-carbon in N-isopropylmethacrylamide both increase the steric effect, making it more difficult for monomers to draw closer and resulting in higher LCST levels of the polymers. In addition, the simulated results from their corresponding oligomers exhibit the similar trend to those from the monomers.

A-Site Distribution in La1−xSrxMnO3: a Computational Study

2008 ◽  
Vol 1074 ◽  
Author(s):  
Yun Hee Jang ◽  
François Gervais ◽  
Yves Lansac
Keyword(s):  
Molecular Dynamics ◽  
Quantum Mechanics ◽  
Colossal Magnetoresistance ◽  
Computational Study ◽  
Mixed Valence ◽  
Magnetic Tunnel Junction ◽  
Md Simulations ◽  
Site Distribution ◽  
Mixed Valence Manganites ◽  
A Site

ABSTRACTThe possibility of an A-site (La3+/Sr2+) ordering in a colossal magnetoresistance manganite (CMR) La3/4Sr1/4MnO3 was explored using molecular dynamics (MD) simulations with a newly developed force field (FF) and quantum mechanics (QM) calculations on the structures obtained from MD. The calculated degrees of stabilization (enthalpy gain) of various patterns of A-site ordering are not significant enough to overcome the accompanying entropy loss, supporting the random A-site distribution in La3/4Sr1/4MnO3. This approach combining MD and QM as well as the versatile FF developed in this study should be useful to investigate the structures and functions of magnetic tunnel junction devices involving mixed-valence manganites.

Site Balance Models in Plasma Processing: A Comparison to Molecular Dynamics Simulations

1995 ◽  
Vol 389 ◽  
Author(s):  
M.E. Barone ◽  
D.B. Graves
Keyword(s):  
Molecular Dynamics ◽  
Steady State ◽  
Molecular Dynamics Simulations ◽  
Phenomenological Models ◽  
Silicon Surface ◽  
Plasma Processing ◽  
Md Simulations ◽  
Balance Model ◽  
Dynamics Simulations ◽  
A Site

ABSTRACTMolecular dynamics (MD) simulations were conducted of Cl+ impact (at 10, 25 and 50 eV) of an initially bare silicon surface, leading to steady state coverage of Cl in a mixed chlorosilyl layer. Our main goal in this study was to compare the MD predictions to models of ion-assisted etching involving the concept of a site balance. For the case of 50 eV Cl+ etching silicon, the coverage vs. exposure results in the simulation could be reasonably well reproduced in a site balance model, but only if the correct parameters in the model were taken from the simulation. The results of the comparison suggest that MD simulations can be helpful in the development of physically sound phenomenological models of ion-assisted etching.

Exploring the hydrated microstructure and molecular mobility in blend polyelectrolyte membranes by quantum mechanics and molecular dynamics simulations

RSC Advances ◽  
2016 ◽  
Vol 6 (42) ◽  
pp. 35517-35526 ◽  
Author(s):  
Ghasem Bahlakeh ◽  
Mohammad Mahdi Hasani-Sadrabadi ◽  
Karl I. Jacob
Keyword(s):  
Molecular Dynamics ◽  
Quantum Mechanics ◽  
Molecular Dynamics Simulations ◽  
Molecular Mobility ◽  
Md Simulations ◽  
Effect Of Water ◽  
Polyelectrolyte Membranes ◽  
Dynamical Behaviors ◽  
Dynamics Simulations ◽  
Water Contents

QMs and MD simulations were employed to investigate the effect of water contents and temperatures on structural and dynamical behaviors of blended PEMs.

scholarly journals Lipase-catalyzed O-acylation of (RS)-propranolol is determined by the acyl group length

2020 ◽  
Author(s):  
Gilberto A. Zapata-Romero ◽  
Markus Doerr ◽  
Martha C. Daza
Keyword(s):  
Molecular Dynamics ◽  
Quantum Mechanics ◽  
Computational Modeling ◽  
Molecular Dynamics Simulations ◽  
Molecular Mechanics ◽  
Hydrocarbon Chain ◽  
Candida Antarctica Lipase ◽  
Ensemble Docking ◽  
Consensus Scoring ◽  
Dynamics Simulations

We employed a computational modeling approach to study the Michaelis complexes of (R)- and (S)-propranolol with serine-acylated Candida antarctica lipase B using four acyl groups: ethanoyl, butanoyl, octanoyl and hexadecanoyl. Our methodology involves sampling Michaelis complex conformations, first through ensemble docking using consensus scoring, and second by molecular dynamics simulations employing a quantum mechanics/molecular mechanics approach. The conformations are then categorized into two classes of near attack conformations, according to the distance of (a) the amino and (b) the hydroxy group of propranolol to the catalytic residues. The relative populations of these two classes of conformations was found to be consistent with the experimentally-observed exclusive chemoselectivity toward O-acylation with ethanoyl. Furthermore, we predict that increasing the length of the hydrocarbon chain of the acyl group will cause O-acylation to be unfavorable.

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