CALCULATION OF FORCES (POTENTIALS)
- Obviously, the best ``potential'' is found from a quantum
mechanical study. These ``ab-initio'' or first principle
potentials can only be applied to
systems of very limited size,
and extremely limited time development.
Next best is something in the spirit of ``tight-binding'' molecular dynamics,
where quantum mechanical effects are included within this approximation.
Manybody potentials assembled from first principle results and
experimental measurements are in wide use for calculations with thousands of
particles for times sufficient to observe many phenomena.
Excellent agreement between manybody potentials
and first principle results can be found, see one example.
- The weakest potentials for general use are the
simple potentials, such as Lennard-Jones. These are great for argon, but do not
give a good approximation to semiconductors or ceramics.
- For carbon modeling we used the
potentials of Tersoff [Phys.Rev.Lett. 61 (1988) 2879]
and Brenner [Phys.Rev.B 42 (1990) 9458]
For vanadium we used the Embedded Atom Potential of
Finnis and Sinclair and for
aluminium we used