No abstract is provided for this article.
No abstract is provided for this article.
No abstract is provided for this article.
Torsion and Lennard-Jones parameters of the optimized potentials for liquid simulations (OPLS) all-atom force field have been refined for describing thermodynamics and dynamics of a wide range of liquid alkanes. Monte Carlo statistical mechanics (MC) and molecular dynamics (MD) simulations were carried out. For thermodynamics properties, MC simulations with truncated electrostatic interactions performed very closely to MD simulations with a Verlet neighbor list and the particle mesh Ewald algorithm. The average errors in comparison with experimental data for computed properties were improved with the modified force field (OPLS/2020), especially for long-chain alkanes. For liquid densities, heats of vaporization, and free energies of hydration, the average errors are 0.01 g/cm3, 0.2 kcal/mol, and ca. 0.5 kcal/mol, respectively; significant gains were made for relative heats of vaporization of isomeric series. Results for self-diffusion coefficients also reproduce experimental data well for linear alkane liquids up to hexadecane. The new force field is suitable for use in improved modeling of myriad systems of importance in chemistry, biology, and materials science.
Die Orbital‐Wechselwirkungen zwischen kleinen Ringen und ungesättigten Brücken werden hinsichtlich der relativen Stabilitäten der Systeme wie z.B. Bicyclo[2.1.l]hexen‐(2) und 2,3‐Dimethylen‐bicyclo[2.
No abstract is provided for this article.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTProton affinities and gas-phase basicities of alkyl and silyl ethersJames F. Blake and William L. JorgensenCite this: J. Org. Chem. 1991, 56, 21, 6052–6059Publication Date (Print):October 1, 1991Publication History Published online1 May 2002Published inissue 1 October 1991https://pubs.acs.org/doi/10.1021/jo00021a018https://doi.org/10.1021/jo00021a018research-articleACS PublicationsRequest reuse permissionsArticle Views153Altmetric-Citations22LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
Deficiencies in energetics obtained using the common semiempirical methods, AM1, PM3, and MNDO, may partly be traced to the use of pseudoatomic equivalents for conversion of molecular energies to heats of formation at 298 K. We present an alternative scheme based on the use of bond and group equivalents. Values for the 61 bond and group equivalents necessary for treatment of molecules containing the common organic elements, hydrogen, carbon, nitrogen, and oxygen have been derived. For a set of 583 neutral, closed‐shell molecules mean absolute errors in AM1, PM3, and MNDO heats of formation are reduced from 6.6, 4.2, and 8.2 kcal/mol to 2.3, 2.2, and 3.0 kcal/mol, respectively. Several systematic problems are overcome in the present scheme including relative stabilities of branched hydrocarbons, energetics of conjugated systems, heats of formation of long chain hydrocarbons, and enthalpies of molecules containing multiple heteroatoms. Although the approach is restricted to molecules with well‐defined functional groups, the equivalents are easy to incorporate and are chemically relevant. This revised procedure allows semiempirical methods to be used for far more reliable evaluations of heats of reactions. Estimates are made of the errors inherent in these semiempirical formalisms, arising from integral approximations and the neglect of explicit treatment of electron correlation effects, while excluding those from inadequate parameterization. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 498–510, 2002; DOI 10.1002/jcc.2002;10023
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAb initio study of the SN2 reactions of hydroxide and hydroperoxide with chloromethaneJeffrey D. Evanseck, James F. Blake, and William L. JorgensenCite this: J. Am. Chem. Soc. 1987, 109, 8, 2349–2353Publication Date (Print):April 1, 1987Publication History Published online1 May 2002Published inissue 1 April 1987https://pubs.acs.org/doi/10.1021/ja00242a018https://doi.org/10.1021/ja00242a018research-articleACS PublicationsRequest reuse permissionsArticle Views481Altmetric-Citations63LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
The 2013 Nobel Prize in Chemistry has been awarded to Martin Karplus, Michael Levitt, and Arieh Warshel for “development of multiscale models for complex chemical systems.” The honored work from the 1970s has provided a foundation for the widespread activities today in modeling organic and biomolecular systems.
