Re: CCL:Ab-initio Force Constants

 > Ab-initio frequency calculations give
 > force constants in cartesian and internal
 > coordinates, the units being respectively
 > hartree/bohr (and not hartree/bohr**2) and
 > atomic units.
 Wrong, the unit of force constants in cartesian
 coordinates is hartree/bohr**2 (which is an atomic
 unit). The unit of force constants in internal coordinates
 depends on the types of internal coordinates involved
 in the force constant, if it is a bend-bend the unit is
 hartree/bohr**2, if it is a angle-bend the unit is
 hartree/(bohr*rad), and if it is an angle-angle the unit
 is hartree/rad**2.
 > Does somebody know how to
 > convert them in mdyn/angstrom?
 1 hartree/bohr**2 = 15.5691905 mdyn/Ang
 1 hartree/(bohr*rad) = 8.2388584 mdyn
 1 hartree/rad**2 = 4.3598149 mdyn*Ang
 Joerg-R. Hill
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