Cartesian vs HDLC

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Cartesian vs HDLC

Hello Everyone,

I noticed that there is about 18kcal/mol difference between the energies that I obtain with doing optimisation in Cartesian & HDLC coordinates. Why is there such a huge difference ? E (cartesian) - E(hdlc) ~ 18kcal/mol. And should I optimise all of my structures using the same coordinate system now ?

-Thank you

tomkeal's picture
Cartesian vs HDLC


It's sensible to use a consistent coordinate system when optimising a group of structures but in principle they will converge to the same value up to the limit of the convergence threshold you have set. The most likely explanation for the difference you are seeing is that the two optimisations you have run have found two different local minima, which is always possible on any reasonably complex potential energy surface. You may be able to see the difference by visualising the structures.

Best wishes,


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