RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I.

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I. Research Abstract Details 

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RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I. Abstract Text:

Gerd B Rocha,Ricardo O Freire,Alfredo M Simas,James J P Stewart,

Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability--being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be improved if the full potential of new linear scaling techniques, such as MOZYME and LocalSCF, is to be realized. Accordingly, in this article we present RM1 (Recife Model 1): a reparameterization of AM1. As before, the properties used in the parameterization procedure were: heats of formation, dipole moments, ionization potentials and geometric variables (bond lengths and angles). Considering that the vast majority of molecules of importance to life can be assembled by using only six elements: C, H, N, O, P, and S, and that by adding the halogens we can now build most molecules of importance to pharmaceutical research, our training set consisted of 1736 molecules, representative of organic and biochemistry, containing C, H, N, O, P, S, F, Cl, Br, and I atoms. Unlike AM1, and similar to PM3, all RM1 parameters have been optimized. For enthalpies of formation, dipole moments, ionization potentials, and interatomic distances, the average errors in RM1, for the 1736 molecules, are less than those for AM1, PM3, and PM5. Indeed, the average errors in kcal x mol(-1) of the enthalpies of formation for AM1, PM3, and PM5 are 11.15, 7.98, and 6.03, whereas for RM1 this value is 5.77. The errors, in Debye, of the dipole moments for AM1, PM3, PM5, and RM1 are, respectively, 0.37, 0.38, 0.50, and 0.34. Likewise, the respective errors for the ionization potentials, in eV, are 0.60, 0.55, 0.48, and 0.45, and the respective errors, in angstroms, for the interatomic distances are 0.036, 0.029, 0.037, and 0.027. The RM1 average error in bond angles of 6.82 degrees is only slightly higher than the AM1 figure of 5.88 degrees, and both are much smaller than the PM3 and PM5 figures of 6.98 degrees and 9.83 degrees, respectively. Moreover, a known error in PM3 nitrogen charges is corrected in RM1. Therefore, RM1 represents an improvement over AM1 and its similar successor PM3, and is probably very competitive with PM5, which is a somewhat different model, and not fully disclosed. RM1 possesses the same analytical construct and the same number of parameters for each atom as AM1, and, therefore, can be easily implemented in any software that already has AM1, not requiring any change in any line of code, with the sole exception of the values of the parameters themselves.

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I. Publishing Authors By Initials

GB Rocha,RO Freire,AM Simas,JJ Stewart,

For similar natural sciences: science: models, theoretical: models, chemical research abstracts see: natural sciences: science: models, theoretical: models, chemical research

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RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I. Journal Published:

PUBLICATION TYPE: Research Support, Non-U.S. Gov

Journal: Journal of computational chemistry

VOLUME: 27

Page Numbers: 1101-11

Journal Abbreviation:

ISSN: 0192-8651

DAY: 30

MONTH: Jul

YEAR: 2006

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I. Information

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LANGUAGE: eng

NlmUniqueID: 9878362

RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I. Keywords Mesh Terms:

KEYWORDS: Models, Chemical

MESH TERMS: chemistry

Chemical & Substance for Abstract: RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I. Information

Substance Name: Ions

Registry Number: 0

Grant and Affiliation Information for RM1: a reparameterization of AM1 for H, C, N, O, P, S, F, Cl, Br, and I.

AFFILIATION: Departamento de Química Fundamental, CCEN, UFPE, 50590-470, Recife PE, Brazil.

Country: United States

AGENCY: United States NIGMS

GRANT: 2 R44 GM067237-02

ACRONYM: GM

MEDLINETA: J Comput Chem

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