[Pw_forum] QM/MM and/or external charges in QE

[Michael Sullivan]

PWSCFers:

My colleague has this question/problem:

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We have a cluster of atoms (not necessarily periodical). One (small) region of this cluster must be treated by Quantum Mechanics, the rest can be treated semiclassically or classically. As in QM/MM, the semiclassical/classical calculation is performed first and the result is a spatial charge distribution. For the QM calculation, we need to do DFT considering the influence of the semiclassical/classical charge distribution.

Would Quantum Espresso be able to handle DFT in the external electrostatic field created by the above-mentioned charge distribution? If the answer is yes, how do we technically do it?
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The related question that I have is this: Is there any way to introduce point charges into the DFT? This makes for a simple QM/MM method. Do we need to work out the electric field itself and input that in using something like tefield or lefield?

Also, is there any work being done on interfacing QE with some MM package like what CPMD does with GROMACS (in what seems to be a rather clunky way)?

Thanks for your help,

Mike Sullivan
michael at ihpc.a-star.edu.sg
http://www.ihpc.a-star.edu.sg/


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