Merck molecular force field MMFF

Inadequate availability of experimental data can considerably inhibit the development of improved energy functions for more accurate simulations of energetic, structural, and spectroscopic properties. This has led to the development of class II force fields such as CFF and the Merck Molecular Force Field (MMFF), which are both based primarily on quantum mechanical calculations of the energy surface. The purpose of MMFF, which has been developed by Thomas Halgren at Merck and Co., is to be able to handle all functional groups of interest in pharmaceutical design. 

The Merck molecular force field (MMFF) is one of the more recently published force fields in the literature. It is a general-purpose method, particularly popular for organic molecules. MMFF94 was originally intended for molecular dynamics simulations, but has also seen much use for geometry optimization. It uses five valence terms, one of which is an electrostatic term, and one cross tenn. 

These potential energy terms and their attendant empirical parameters define the force field (FF). More complicated FFs which use different and/or more complex functional forms are also possible. For example, the simple harmonic oscillator expression for bond stretching can be replaced by a Morse function, Euorse (3), or additional FF terms may be added such as the stretch-bend cross terms, Estb, (4) used in the Merck molecular force field (MMFF) (7-10) which may be useful for better describing vibrations and conformational energies. 

Merck molecular force field (MMFF) calculations were performed for octahydrobenzoM[l,3,6]trioxocine (Equation 1 <1999MRC401>). They indicated a preference of ca. 1.8kJmol 1 for the most populated conformation 3b, which is in reasonable agreement with 13C NMR experimental value of 4.4 kj mol-1. In the preferred conformer, the... 

Over the past years the search for more reliable discrimination of L/M relative steric size and theoretical prediction of the preferred interporphyrin helicity of the host—guest complex has led to the development of molecular mechanics calculations protocol using the Merck Molecular Force Field (MMFF) approach coupled to Monte Carlo-based conformational analysis.57... 

Cheng A, Best SA, Merz KM Jr., Reynolds CH. GB/SA water model for the Merck molecular force field (MMFF). J Mol Graphics Modell 2000 18 273-282. 

The Merck Molecular Force Field (MMFF) uses a generalized Lennard-Jones potential where the exponents and two empirical constants are derived from experimental data for rare gas atoms." The resulting buffered 14-7 potential is shown in eq. (2.14). 

Figure 13 (a) Conformational behavior of 43, and Merck Molecular Force Field (MMFF)-minunized geometries of (b) 43c, (c) cross-... 

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