initial hesse matrix
in order to set up an initial hesse matrix for geometry optimizations
built up from a simple valence force field (see e.g. H.B.Schlegel,
Theoret.Chim.Acta 66,333,(1984)) I have written a short routine
that establishes valence coordinates from a given set of
cartesian coordinates. Whether there is a bond or not between
a pair of atoms is determined by a set of covalent radii
and two parameters which I have taken from a piece of code
written by T.A.Halgren ('NABOR').
Since I have no idea how old this piece of code might be, I would
like to know if there is a standard set of covalent radii somewhere
and perhaps also a standard rule which tells me if there is a bond
between two atoms or not using these covalent radii.
Thank you very much in advance,
Lehrstuhl f. Theoret. Chemie