Units used for Step & Gradient in chemshell

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Units used for Step & Gradient in chemshell

Hi All,

What are the units used for Step and Grad in chemshell ?
and is it mentioned anywhere in the chemshell doc, couldnt find it.
Waiting for reply ,


ylu's picture


they are in a.u.. ChemShell converts results from external QM or MM codes to be used for DL_FIND if they are not in atomic units already. This is also described in the manual:

Thank you for using ChemShell!


Units in which it is printed in log file.

Just a confirmation , so the units in which the results are printed in the log file are they also in a.u ?

Awaiting reply.
Thank you.

ylu's picture
Yes, in a.u. unless pointed

Yes, in a.u. unless pointed out otherwise. For example, an exception is the built-in DL_POLY Classic which prints energies in kcal/mol:
4368 MM Energies (kcal/mol) total : -3.60275164E+03
4369 short range: -4.03151080E+02 coulombic : -5.69392315E+03 3body : 0.00000000E+00
4370 bond : 5.74345423E+02 angle : 8.04517370E+02 str-bend : 0.00000000E+00
4371 per dihed : 1.01302448E+03 harm dihed : 1.88736549E+01 angle-angle: 0.00000000E+00
4372 ang-ang-tor: 0.00000000E+00 urey-brdly : 8.35616583E+01 inversion : 0.00000000E+00

But the QM/MM energy is still converted to a.u.

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