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Re: Geometry optimization using Cartesian coordinates

Alex Granovsky

Dear Patrick,

Firefly does not allow internal coordinates with electric field
because internal coordinates eliminate the rotational degrees
of freedom, which are no longer free.

For electric field computations I'd suggest you to increase
ICUT by 1-2 digits, and tighten NCONV to at least 6 or maybe even 7.

Kind regards,
Alex Granovsky

On Wed Dec 24 '14 5:05am, Patrick SK Pang wrote
>I am now doing geometry optimization of molecules under electric field, and the Firefly program allows me to use Cartesian coordinates only. I find that it is difficult to locate the optimized geometries because the RMS gradient always oscillates even I did the Hessian calculation first. Could anyone suggest methods to solve the problem?

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