A fortran program in which Tirion's model (also called the Elastic Network
Model) is implemented. Within the frame of this model, atoms (particles)
less than cutoff (angstroms) away from each others are linked by springs of
same strength. Alternatively, a list of interacting atoms can be given to the
Requirements: a file with the coordinates of the system, in PDB (Protein Data
Bank) or "x y z mass" format.
Output: the hessian (the mass-weighted second derivatives of energy matrix),
in the "i j non-zero-ij-matrix-element" format.
Diagstd, a fortran program with a standard diagonalization routine, can next
be used in order to obtain the corresponding normal modes of the system. If
the system is large, the RTB approximation can prove usefull (see below).