Donald L. Thompson's Theoretical Chemistry Group Department of Chemistry, Schlundt Hall, University of Missouri - Columbia

	GenDyn A General Trajectory Code A Brief Description
	GenDyn calculates classical trajectories for molecular systems by numerical integration of Hamilton's equations of motion. The program is general in that a wide variety of problems may be treated through appropriate specifications in user-generated bonds, and angles; force constants; and equilibrium values of the internal coordinates or the equilibrium Cartesian coordinates. The potential energy surface can be defined using valence internal coordinates. Standard potential energy functions are options in the code. Internal coordinate options are covalent bonds, covalent bond angles, wag angles, and harmonic or anharmonic (i.e., Morse function). The bond and wag angles are treated harmonically, dihedral interactions are represented by six-term cosine series, and interactions between nonbonded atoms by Lennard-Jones functions. The code is easily adapted to include other potential energy functions or modifications of existing ones, such as attenuation of the potential energy surface (i.e., switching) as a simultaneous function of one or several reaction coordinates. Normal-mode analysis of the potential energy surface is done using analytical second derivatives. A variety of methods are included for the specification of initial conditions for the microcanonical ensemble, including normal-mode excitation, X-H local-mode excitation (X=heavy atom), Metropolis shell sampling, and efficient microcanonical sampling. Sampling the canonical ensemble is done by using a thermal excitation scheme. The code contains options for analysis of the trajectories. Local and/or normal-mode energies may be calculated during the course of the trajectories with automatic averaging over an ensemble (assuming non-reactive dynamics). Rate constants can be calculated for first-order processes. The code is structures such that the output can be easily altered and external subroutines can be used assist in the analysis of the computed results.      Many of the methods used in GenDyn are described in: T. D. Sewell and D. L. Thompson, International Journal of Modern Physics, 11(9), 1067-1112 (1997). Further information about the code may be obtained by contacting Don Thompson at thompsondon@missouri.edu. Download GenDyn Maunual (click here) Download GenDyn Code (click here) (490kB TAR File)

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