"Morphing" of ab initio-based interaction potentials to spectroscopic accuracy: Application to Cl-(H2O)

2004 ◽  
Vol 76 (1) ◽  
pp. 29-35 ◽  
Author(s):  
J. M. Bowman ◽  
S. S. Xantheas
Keyword(s):  
Ab Initio ◽  
Interaction Potential ◽  
Vibrational Spectra ◽  
Mode Coupling ◽  
Effective Means ◽  
Intermolecular Potentials ◽  
Average Absolute Deviation ◽  
Absolute Deviation ◽  
Water Interaction ◽  
Chloride Water

We present anharmonic vibrational calculations for the Cl-(H2O) cluster and their convergence with the n-mode representation of the interaction potential. Extension of this representation up to 4-mode couplings produces results that appear to be converged to within 10 cm-1 or less relative to the exact 6-mode representation for this system. This methodology, in conjunction with the "morphing" technique, which is based on the scaling of the internal coordinates, provides an effective means of fitting intermolecular potentials to measured vibrational spectra. Application of this approach to the chloride-water interaction produces a revision of a previously developed empirical interaction potential that reproduces the measured fundamental and first overtone frequencies to within an average absolute deviation of 1.75 cm-1 in the 4-mode coupling representation.

scholarly journals High precision evaluation of the combustion enthalpy by ab-intio computations

2021 ◽  
Author(s):  
Amin Alibakhshi
Keyword(s):  
Ab Initio ◽  
Ab Initio Methods ◽  
Average Absolute Deviation ◽  
Absolute Deviation ◽  
Accurate Evaluation ◽  
Combustion Enthalpy ◽  
Ab Initio Computation ◽  
Precise Evaluation ◽  
Precision Evaluation ◽  
Empirical Corrections

Accurate evaluation of combustion enthalpy is of high scientific and industrial importance. Although via ab-initio computation of heat of reactions, as one of the promising and well-established approaches in computational chemistry, this goal should in principle be achievable, examples of reliable and precise evaluation of heat of combustion by ab-initio methods has surprisingly not yet been reported. A handful of works carried out for this purpose report significant inconsistencies between the ab-initio evaluated and experimentally determined combustion enthalpies and suggest empirical corrections to improve the accuracy of predicted data. With this background, the main aims of the present study is to investigate the reasons behind those reported inconsistencies and propose guidelines for highly accurate evaluation of combustion enthalpy via ab-initio computations. Through the provided guidelines, the most accurate results ever reported, with average absolute deviation, mean unsigned error and correlation coefficient of 1.556 kJ/mole, 0.072% and 0.99999, respectively, is achieved for theoretically computed combustion enthalpies of 40 studied hydrocarbons.

Vibrational spectra of stannane: Harmonic force field, Raman and IR intensities from ab initio correlated wavefunctions

1989 ◽  
Vol 130 (1-3) ◽  
pp. 451-456 ◽  
Author(s):  
Javier Fernandez Sanz ◽  
Antonio Marquez ◽  
Claude Pouchan
Keyword(s):  
Force Field ◽  
Ab Initio ◽  
Vibrational Spectra ◽  
Harmonic Force ◽  
Ir Intensities

Constructing accurate interaction potentials to describe the microsolvation of protonated methane by helium atoms

2017 ◽  
Vol 19 (12) ◽  
pp. 8307-8321 ◽  
Author(s):  
Dennis Kuchenbecker ◽  
Felix Uhl ◽  
Harald Forbert ◽  
Georg Jansen ◽  
Dominik Marx
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Ab Initio ◽  
Path Integral ◽  
Interaction Potential ◽  
Stationary Point ◽  
Path Integral Monte Carlo ◽  
Interaction Potentials ◽  
Helium Atoms

An ab initio-derived interaction potential is derived and used in path integral Monte Carlo simulations to investigate stationary-point structures of CH5+ microsolvated by up to four helium atoms.

Solubility of the pesticide diuron in organic nonelectrolyte solvents. Comparison of observed vs. predicted values based upon Mobile Order theory

2000 ◽  
Vol 78 (2) ◽  
pp. 184-190 ◽  
Author(s):  
Karina M De Fina ◽  
Tina L Sharp ◽  
Michael A Spurgin ◽  
Ivette Chuca ◽  
William E Acree, Jr. ◽  
...  
Keyword(s):  
Order Theory ◽  
Average Absolute Deviation ◽  
Absolute Deviation ◽  
Solubility Predictions ◽  
Mobile Order Theory ◽  
Dimethyl Urea ◽  
Organic Nonelectrolyte ◽  
Predicted Values ◽  
Alcohol Solvents ◽  
Mobile Order

Experimental solubilities are reported at 25.0°C for diuron (also called 3-(3,4-dichlorophenyl)-1,1-dimethyl urea) dissolved in 49 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, ester-, methyl-, and tert-butyl-functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 28 nonalcoholic solvents for which predictions could be made computations show that Mobile Order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 60.1%. Diuron solubilities in the alcohol solvents are used to calculate stability constants for presumed solute-solvent hydrogen bonds that are believed to occur in solution.Key words: pesticide, diuron solubilities, organic nonelectrolyte solvents, solubility predictions.

Conformational stability, vibrational spectra and ab initio calculations for chloromethyl methyl silane and chloromethyl methyl difluorosilane

1999 ◽  
Vol 480-481 ◽  
pp. 147-151 ◽  
Author(s):  
Gamil A. Guirgis ◽  
Yasser E. Nashed ◽  
James B. Robb II ◽  
Peter Klaeboe ◽  
Pengqian Zhen ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Vibrational Spectra ◽  
Conformational Stability

Structural stabilities and transformations in cationized asparagine at finite temperatures: An ab initio molecular dynamics study

2014 ◽  
Vol 13 (04) ◽  
pp. 1450024
Author(s):  
Shoutian Sun ◽  
Jianwen Liu ◽  
Zhi-Feng Liu
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Structural Transformation ◽  
Vibrational Spectra ◽  
Room Temperature ◽  
Ab Initio Molecular Dynamics ◽  
And Shifts ◽  
Torsional Angles

The cationic complexes of Asparagine (Asn), M +( Asn ), with M + = Li +, Na +, K +, Cs +, and H +, are models for studying the interaction between cations and Asn. Ab initio molecular dynamics (AIMD) method is employed to simulate their behavior at finite temperatures. Structural transformation between conformers is observed, which becomes progressively easier as the cation varies from Li +, to Na +, K +, Cs +, and H +. The fluctuation of the M +– N and M +– O distances and rotation of torsional angles are significant even at room temperature for K +, Cs + and H +. Vibrational profiles based on AIMD trajectories provide insights into the broadening and shifts in relative intensities observed in the vibrational spectra measured by infrared multi-photon dissociation (IRMPD) experiments.

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