[molpro-user] Units of mass weighted 2nd derivative matrix

[David Danovich]

Hello,

In the output of molpro (when asked to print hessian)  there is a line for
force constant

"Force Constants (Second Derivatives of the Energy) in [a.u.]"

which is given in au.


For the mass weighted 2nd derivative matrix molpro also prints eigenvalues

"Mass Weighted 2nd Derivative Matrix Eigenvalues"

For the C2 molecule (ground state singlet) I got values of 0.131024. What
are the units of it and how can I convert this value to N/cm?   Using simple
formula

v(cm-1)=(1/2Pi*c)*Sqrt(f(m1+m2)/(m1*m2))

 one can get value for force constant (f) using wave number obtained from
frequency calculations. Using this formula I got value of 12.2 N/cm.
How can I get something similar from eigenvalues of molpro output?

Thank you  David
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