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.

"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.

Determination of acidic dissociation constants of L-phenylalanyl-glycine and L-alanyl-L-alanine in water using ab initio methods

2014 ◽  
Vol 2 (42) ◽  
pp. 263-263
Author(s):  
Farhoush Kiani ◽  
Mahmoud Tajbakhsh ◽  
Fereydoon Ashrafi ◽  
Nesa Shafiei ◽  
Azar Bahadori ◽  
...  
Keyword(s):  
Ab Initio ◽  
Dissociation Constants ◽  
Ab Initio Methods ◽  
Acidic Dissociation

Study of the structure and stability of aqua ions La(H2O) n 3+ (n = 8, 9) by ab initio methods

2008 ◽  
Vol 53 (8) ◽  
pp. 1249-1255 ◽  
Author(s):  
V. Yu. Buz’ko ◽  
I. V. Sukhno ◽  
M. B. Buz’ko ◽  
A. A. Polushin ◽  
V. T. Panyushkin
Keyword(s):  
Ab Initio ◽  
Ab Initio Methods ◽  
Structure And Stability

Ab initio computation of interband contribution to the optical conductivity of YBa2Cu3O7−x

1988 ◽  
Vol 153-155 ◽  
pp. 1239-1240
Author(s):  
S.T. Chui ◽  
Robert V. Kasowski ◽  
William Y. Hsu
Keyword(s):  
Ab Initio ◽  
Optical Conductivity ◽  
Ab Initio Computation

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.

Ab Initio Computation of Thermochemistry and Kinetics in the Oxidation of Gas Phase Silicon Species

1992 ◽  
Vol 282 ◽  
Author(s):  
Michael R. Zachariah ◽  
Wing Tsang
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Energy Barrier ◽  
Reaction Rate ◽  
Rate Theory ◽  
Molecular Orbital Calculations ◽  
Activation Energy Barrier ◽  
Ab Initio Computation ◽  
Oxygen Donor ◽  
Reaction Rate Theory

ABSTRACTAb initio molecular orbital calculations coupled to RRKM reaction rate theory have been conducted on some important reactions involved in the oxidation of silane in a high-temperature/high H2O environment. The results indicate thatH2O acts as an oxygen donor to SiH2 to form H3SiOH or SiH2O. Subsequent reactions involve the formation of (HSiOOH, H2Si(OH)2,:Si(OH)2 or SiO). In turn SiO polymerizes into planar rings, without an activation energy barrier. A list of calculated thermochemical data are also presented for a number of equilibrium species.

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