ChemInform Abstract: VERBRENNUNGSWAERMEN UND SPANNUNGSENERGIEN VON BICYCLO(N,M,0)ALKANEN

McNally, Donal; Shary‐Tehrany, Shahrokh; Hickey, Mary James; Boyd, Richard H.

doi:10.1002/chin.197033168

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“…This term, which is independent of the torsion angle, is more clearly seen by rewriting eq. (17) as (18) The restoring force on the bond is therefore given by -dEldb = -k -k cos 34 (19) Thus, the first term in eq. (18) is a linear term that is effectively added to the polynomial in eq.…”

Section: Bond/'i'oksion and Angle/iohsion Couplingmentioning

confidence: 99%

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

Maple¹,

Hwang²,

Stockfisch³

et al. 1994

J Comput Chem

790

547

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A new method for deriving force fields for molecular simulations has been developed. It is based on the derivation and parameterization of analytic representations of the ab initio potential energy surfaces. The general method is presented here and used to derive a quantum mechanical force field (QMFF) for alkanes. It is based on sampling the energy surfaces of 16 representative alkane species. For hydrocarbons, this force field contains 66 force constants and reference values. These were fit to 128,376 quantum mechanical energies and energy derivatives describing the energy surface. The detailed form of the analytic force field expression and the values of all resulting parameters are given. A series of computations is then performed to test the ability of this force field to reproduce the features of the ab initio energy surface in terms of energies as well as the first and second derivatives of the energies with respect to molecular deformations. The fit is shown to be good, with rms energy deviations of less than 7% for all molecules. Also, although only two atom types are employed, the force field accounts for the properties of both highly strained species, such as cyclopropane and methylcyclopropanes, as well as unstrained systems. The information contained in the quantum energy surface indicates that it is significantly anharmonic and that important intramolecular coupling interactions exist between internals. The representation of the nature of these interactions, not present in diagonal, quadratic force fields (Class I force fields), is shown to be important in accounting accurately for molecular energy surfaces. The Class I1 force field derived from the quantum energy surface is characterized by accounting for these important intramolecular forces. The importance of each 'Author to whom all correspondence should be addressed. tl'resent address: Dept. of Chemistry, Ben Gurion Univ. of the Negev, Beersheva 84105, Israel. Journal of Computational DERIVATION OF CLASS II FORCE FIELDSof the interaction terms of the potential energy function has also been assessed. Bond anharmonicity, angle anharmonicity, and bond/angle, bond/ torsion, and angle/angle/ torsion cross-term interactions result in the most significant overall improvement in distorted structure energies and energy derivatives. The implications of each energy term for the development of advanced force fields is discussed. Finally, it is shown that the techniques introduced here for exploring the quantum energy surface can be used to determine the extent of transferability and range of validity of the force field. The latter is of crucial importance in meeting the objective of deriving a force field for use in molecular mechanics and dynamics calculations of a wide range of molecules often containing functional groups in novel environments.

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Section: Bond/'i'oksion and Angle/iohsion Couplingmentioning

confidence: 99%

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

Maple¹,

Hwang²,

Stockfisch³

et al. 1994

J Comput Chem

790

547

View full text Add to dashboard Cite

show abstract

ChemInform Abstract: VERBRENNUNGSWAERMEN UND SPANNUNGSENERGIEN VON BICYCLO(N,M,0)ALKANEN

Abstract: Die Verbrennungswärmen, Dampfdrücke, spezifischen Wärmen in der Flüssigphase, Bildungswärmen und Spannungsenergien der Bicyclen (I)‐(III) werden bestimmt.

Cited by 1 publication

References 1 publication

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

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