A Force Field for Phosphoric Acid:  Comparison of Simulated with Experimental Data in the Solid and Liquid State

2000 ◽  
Vol 104 (31) ◽  
pp. 7333-7338 ◽  
Author(s):  
Stéphane A. H. Spieser ◽  
Bas R. Leeflang ◽  
Loes M. J. Kroon-Batenburg ◽  
Jan Kroon
Keyword(s):  
Experimental Data ◽  
Phosphoric Acid ◽  
Force Field ◽  
Liquid State ◽  
Acid Comparison

scholarly journals Optimized Mapping of Gas-Phase Quantum Calculations to General Force Field Lennard-Jones Parameters Based on Liquid-State Data

2019 ◽  
Author(s):  
Samuel Kantonen ◽  
Hari S. Muddana ◽  
Niel M. Henriksen ◽  
Lee-Ping Wang ◽  
Michael Gilson
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Gas Phase ◽  
Liquid State ◽  
Quantum Calculations ◽  
Minimal Basis ◽  
State Data ◽  
Lennard Jones ◽  
Mapping Parameters ◽  
General Force

We utilize a previously described Minimal Basis Iterative Stockholder (MBIS) method to carry out an atoms-in-molecules partitioning of electron densities. Information from these atomic densities is then mapped to Lennard-Jones parameters using a set of mapping parameters much smaller than the typical number of atom types in a force field. This approach is advantageous in two ways: it eliminates atom types by allowing each atom to have unique Lennard-Jones parameters, and it greatly reduces the number of parameters to be optimized. We show that this approach yields results comparable to those obtained with the typed GAFF force field, even when trained on a relatively small amount of experimental data.

scholarly journals Optimized Mapping of Gas-Phase Quantum Calculations to General Force Field Lennard-Jones Parameters Based on Liquid-State Data

2019 ◽  
Author(s):  
Samuel Kantonen ◽  
Hari S. Muddana ◽  
Niel M. Henriksen ◽  
Lee-Ping Wang ◽  
Michael Gilson
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Gas Phase ◽  
Liquid State ◽  
Quantum Calculations ◽  
Minimal Basis ◽  
State Data ◽  
Lennard Jones ◽  
Mapping Parameters ◽  
General Force

We utilize a previously described Minimal Basis Iterative Stockholder (MBIS) method to carry out an atoms-in-molecules partitioning of electron densities. Information from these atomic densities is then mapped to Lennard-Jones parameters using a set of mapping parameters much smaller than the typical number of atom types in a force field. This approach is advantageous in two ways: it eliminates atom types by allowing each atom to have unique Lennard-Jones parameters, and it greatly reduces the number of parameters to be optimized. We show that this approach yields results comparable to those obtained with the typed GAFF force field, even when trained on a relatively small amount of experimental data.

Force field for in-plane vibrations of terephthalonitrile

1989 ◽  
Vol 54 (1) ◽  
pp. 18-27 ◽  
Author(s):  
Juan F. Arenas ◽  
Juan I. Marcos ◽  
Francisco J. Ramírez
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Normal Coordinates ◽  
Internal Coordinates ◽  
Isotopic Shifts ◽  
Quadratic Force Field ◽  
Semi Empirical

The general quadratic force field for the in-plane vibrations of terephthalonitrile was calculated by the semi-empirical MINDO/3 method. This force field was refined to the frequencies observed experimentally for terephthalonitrile and isotopic shifts of terephthalonitrile-[15N2]. The refined frequencies reproduce the experimental data with errors less than 0.5%. The normal coordinates and the force field in internal coordinates were also calculated from the refined field.

scholarly journals Kinetic Modelling and Optimizing of Butyl Propionate over a Synthesied Material (Tungstan Phosphoric Acid) Heteropoly Catalyst Using Response Surface Technique

2021 ◽  
Vol 45 (4) ◽  
pp. 273-280
Author(s):  
Raju Kalakuntala ◽  
Srinath Surnani
Keyword(s):  
Experimental Data ◽  
Phosphoric Acid ◽  
Response Surface ◽  
Kinetic Modelling ◽  
Quadratic Model ◽  
Molar Ratio ◽  
Catalyst Loading ◽  
Response Surface Technique ◽  
Optimized Conditions ◽  
Surface Technique

The performance of heteropoly acid i.e., Tungstan phosphoric acid for the synthesis of butyl propionate at optimized conditions. Effect on conversion and yield of propionic acids using the Response Surface Methodology (RSM) were evaluated by different process parameters including catalyst loading, alcohol/acid molar ratio. There were no external and internal mass transmission limits. A quadratic model acquired by the variance study (ANOVA) has been shown to view experimental data successfully with the regression (R2 = 0.94 and R2 = 0.942) coefficients approaching to unity. The pseudo homogeneous kinetic model (PH) validated with experimental data to determine kinetic parameters i.e., activation energy (45.97 kJ/mol) and frequent factor (91319 L/mol-min).

scholarly journals A hierarchical Bayesian framework for force field selection in molecular dynamics simulations

2016 ◽  
Vol 374 (2060) ◽  
pp. 20150032 ◽  
Author(s):  
S. Wu ◽  
P. Angelikopoulos ◽  
C. Papadimitriou ◽  
R. Moser ◽  
P. Koumoutsakos
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Force Field ◽  
Computational Cost ◽  
Md Simulations ◽  
Bayesian Framework ◽  
Underlying Structure ◽  
Hierarchical Bayesian ◽  
Wide Range ◽  
Selection Of

We present a hierarchical Bayesian framework for the selection of force fields in molecular dynamics (MD) simulations. The framework associates the variability of the optimal parameters of the MD potentials under different environmental conditions with the corresponding variability in experimental data. The high computational cost associated with the hierarchical Bayesian framework is reduced by orders of magnitude through a parallelized Transitional Markov Chain Monte Carlo method combined with the Laplace Asymptotic Approximation. The suitability of the hierarchical approach is demonstrated by performing MD simulations with prescribed parameters to obtain data for transport coefficients under different conditions, which are then used to infer and evaluate the parameters of the MD model. We demonstrate the selection of MD models based on experimental data and verify that the hierarchical model can accurately quantify the uncertainty across experiments; improve the posterior probability density function estimation of the parameters, thus, improve predictions on future experiments; identify the most plausible force field to describe the underlying structure of a given dataset. The framework and associated software are applicable to a wide range of nanoscale simulations associated with experimental data with a hierarchical structure.

Symmetry Coordinates and Tentative Force Field Analysis of a PMo12O40 Model with the Keggin Structure

1976 ◽  
Vol 31 (12) ◽  
pp. 1589-1600 ◽  
Author(s):  
Lennart Lyhamn ◽  
S. J. Cyvin ◽  
B. N. Cyvin ◽  
J. Brunvoll
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Force Constant ◽  
Raman Spectra ◽  
Vibrational Analysis ◽  
Field Analysis ◽  
Infrared And Raman Spectra ◽  
Symmetry Coordinates ◽  
Force Field Analysis ◽  
Complex Ion

Abstract A complete vibrational analysis is performed for the 53 atomic PMo12O40 model of Td symmetry. The symmetry coordinates are classified into those of (a) ligand vibrations, (b) framework-ligand couplings, (c) framework vibrations, and (d) interligand vibrations. Simple valence force fields are estimated, and the influence of inclusion of redundancies on the calculated frequencies and symmetry force constants is investigated. Comments are made on calculated symmetry force constant values up to 345 mdyne/Å. Vibrational frequencies are calculated for the Mo3O7 and Mo3O13 units and for the PMo12O403- complex ion. For the latter compound the calculated values are compared with experimental data from infrared and Raman spectra.

scholarly journals Über die Konformation yon 1.2.4.5-Tetrathian / On the Conformation of 1,2,4,5-Tetrathiane

1982 ◽  
Vol 37 (2) ◽  
pp. 234-235 ◽  
Author(s):  
Rudy Susilo ◽  
Rolf Gmelin
Keyword(s):  
Experimental Data ◽  
Nmr Spectroscopy ◽  
Force Field ◽  
Excellent Agreement ◽  
Dynamic Nmr ◽  
Force Field Calculations ◽  
Chair Form ◽  
Dynamic Nmr Spectroscopy ◽  
Twist Form

Abstract The conformation of 1,2,4,5-tetrathian was determined by means of dynamic NMR spectroscopy. The barrier (ilG+) of the chair/twist equilibration is 14.5 kcal/mol and the chair form is more stable than the twist form in this molecule by 1.4 kcal/mol. These experimental data are in excellent agreement with force field calculations

scholarly journals Elastic, Mechanical, and Phonon Behavior of Orpiment Arsenic Trisulfide under Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Liwu Jiang ◽  
Meiling Wu ◽  
Peng Shi ◽  
Chuanhui Zhang
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Force Field ◽  
Elastic Constants ◽  
Phonon Dispersion ◽  
Geometry Optimization ◽  
Elastic Parameters ◽  
Arsenic Trisulfide ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

Arsenic trisulfide (As2S3) has been found to be an excellent glass former at high temperature and pressure. However, there is still some scarcity for the elastic and phonon behavior of the orpiment phase. By using the Dreiding force field of the geometry optimization computations, we investigated the elastic constants, mechanical moduli, and the phonon dispersion of orpiment As2S3 under the pressure from 0 to 5 GPa. Some results of the elastic parameters of orpiment-As2S3 at 0 GPa are consistent with the experimental data. The phonon dispersions for orpiment As2S3 under pressure are also reasonable with previous calculations.

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