Force Fields A General Discussion

J. R. Maple, Force Fields A General Discussion, in Encyclopedia cf Computational Chemistry (Editor in Chief P. v. Ragu6 ScUeya-), John Wiley Sons, Chichester, 1998, 1017. 

CHARMM The Energy Function and Its Parameterization Force Fields A Brief Introduction Force Fields A General Discussion Force Fields MM3 Force Fields MMFF94 GROMOS Force Field. 

Carbocation Stabilities Comparison of Theory and Experiment Force Fields A General Discussion Mixed Quantum-Classical Methods Molecular Mechanics Conjugated Systems. 

Circular Dichroism Electronic Configuration Interaction Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field Force Fields A Brief Introduction Force Fields A General Discussion Geometry Optimization I Geometry Optimization 2 Infrared Data Correlations with Chemical Structure Intensities of Infrared and Raman Bands Magnetic Circular Dichroism of it Systems Molecular Magnetic Properties. 

AMI AMBER A Program for Simulation of Biological and Organic Molecules CHARMM The Energy Function and Its Parameterization Combined Quantum Mechanics and Molecular Mechanics Approaches to Chemical and Biochemical Reactivity Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field Divide and Conquer for Semiempirical MO Methods Electrostatic Catalysis Force Fields A General Discussion Force Fields CFF GROMOS Force Field Hybrid Methods Hybrid Quantum Mechanical/Molecular Mechanical (QM/MM) Methods Mixed Quantum-Classical Methods MNDO MNDO/d Molecular Dynamics Techniques and Applications to Proteins OPLS Force Fields Parameterization of Semiempirical MO Methods PM3 Protein Force Fields Quantum Mechanical/Molecular Mechanical (QM/MM) Coupled Potentials Quantum Mecha-nics/Molecular Mechanics (QM/MM) SINDOI Parameterization and Application. 

In this article we focus on the use of MM for several reasons. First, most of the molecules considered here are too large to be treated by any other method, and have well-established MM energy functions and parameters (see Force Fields A General Discussion). Second, for a number of systems a MM potential yields the same set of local energy minima as a computationally much more expensive ah initio method, although the relative energies can differ. Third, it may be efficient to find the potentially stable conformations using MM, and then to proceed to their analysis by more... 

MD and MC calculations are the next stage to be used in this area of chemistry. As computers become faster, exclusive MM calculations will be used less often and researchers will shift to the more time-consuming MD and MC computations which are, undoubtedly, much closer to the real situation. Good force fields are required to obtain reliable computational results. Efforts in developing MM force fields have to be continued (see Force Fields A General Discussion). 

Charge Distribution Calculations Alternative Approaches Force Fields A General Discussion Linear Free Energy Relationships (LFER) Population Analyses for Semiempiri-cal Methods Quantitative Structure-Property Relationships... 

Structure and dynamics of molecules includes the geometric structure (interatomic distances and angles) as well as vibrational frequencies, force constants (see Force Fields A General Discussion), barriers to internal rotation, ionization energies, dipole moments, etc. These are intrinsic molecular properties, independent of temperature and pressure. 

Benchmark Studies on Small Molecules Cambridge Structural Database Chemical Engineering Databases Factual Information Databases Force Fields A General Discussion Inorganic Chemistry Databases Quality Control, Data Analysis Rates of Chemical Reactions Spectroscopic Databases. 

This article introduces force fields and Force Fields A General Discussion provides an overview. The articles about specific force fields cover the available widely used force fields, as implemented in various programs. The articles contain explicit discussion of the various ways in which the force fields and the programs containing them are constructed, and the advantages, disadvantages, and the detailed reasons for these choices. 

The CFF differs from empirical force fields (see Force Fields A General Discussion) in that its force constants are derived from a rigorous and generalizable quantum mechanical procedure. This results in a force field that may in principle be applied to any molecular species, independently of the availability of experimental data. The parametrization is then consistent among different types of molecules, permitting more accurate treatment of multifunctional species or molecular complexes, and the amount of quantum mechanical data permits an accurate and detailed form of the energy expression to be parametrized, as described below. 

Biological and Organic Molecules Anharmonic Molecular Force Fields Carbocation Force Fields Carbohydrate Force Fields CHARMM The Energy Function and Its Parameterization Force Fields A Brief Introduction Force Fields A General Discussion Force Fields CFF Force Fields MM3 GROMOS Force Field and OPLS Force Fields). The multitudinous issues related to achieving convergence will be discussed below. 

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