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OS: Linux, Windows

License: Freeware

XMD is a computer program for performing molecular dynamics simulations. It is designed for the simulation of metals and ceramics.

Molecular Dynamics

Constant temperature using velocity re-scaling algorithm (CLAMP command).
Constant pressure using either Andersen's algorithm or a simple volume "rescaling" algorithm suitable for lattice constant versus temperature calculations. (PRESSURE command).
Efficient system relaxation (local minima) algorithm (QUENCH command).
Constrain selected atoms to remain fixed in space (FIX command).
Constrain selected atoms to remain in a line or plane (CONSTRAIN command).
Apply an unique external force to individual atoms (EXTFORCE command).
Tether selected atoms to their initial positions with springs of various spring constants (EXTSPRING command).
Apply velocity damping coefficients to selected atoms (DAMP command).
Uses pair potential, Embedded Atom Method potentials (EAM), Tersoff's Silicon-Carbide potential or Stillinger-Weber Si potential.

Program Input

All program actions are controlled by commands read from one or more text files.
A macro processor lets you enter strings from the command line or define strings within the command file (MACRO command).
A built-in calculator with variables that can be used with all number input (CALC command).
Input file instruct the reading of another input file (READ command).
Flexible creation (FILL command) and editing of atomic structures.
Select subsets of atoms using a variety of patterns (SELECT, SET and TAG commands).
Perform actions on selected atoms, such as moving them (MOVE), inserting defects (SCREW, WAVE), setting atom type (TYPE), setting atom mass (MASS), rotating selected atoms (ROTATE), etc.
Some commands (MOVE, DAMP, EXTFORCE and EXTSPRING) allow input values to be a function of atomic coordinates.

Program Output

Save the complete simulation state for later continuation (WRITE STATE command).
Accumulate system energies (ESAVE and WRITE ENERGY commands), atomic stress (SSAVE and WRITE STRESS commands), atom coordinates (WRITE PARTICLE command) and other information to text files during simulation.
Coordinates can be stored in special compact format (RCV or COR commands) for later use with companion programs such as WMOVIEC which produces movies.
Save atomic coordinates in a Protein Data Bank file for use with display software such as MSI's Cerius2 (WRITE PDB command), or standard XYZ format (WRITE XYZ command).
Built-in plotting routines for plotting atom configuration in color on a Postscript device (PLOT command).