[Pw_forum] relaxation: mistake in finding the lowest energy structure
Stefano de Gironcoli
degironc at sissa.it
Fri Jul 1 18:07:58 CEST 2016
Finding the global minimum of a system may be difficult. Relaxation converge to the nearest local minimum. Chemical intuition may help to make good guesses but sometime it is not enough.
Simulated annealing would be a general purpose very expensive often overkilling never guaranteed approach
Random sampling, Genetic or evolutionary algorithms are other approaches used
(sent from my phone)
> On 01 Jul 2016, at 17:13, ZARA NBSH <z.nrbsh at gmail.com> wrote:
> Dear all,
> I would like to study the interaction between 2 organic molecules (contains O, H, and C atoms).
> As the first step I relaxed the structure (using calculation = 'relax' in &control).
> My problem is that after finishing the run, it could not find the lowest energy structure.
> And I could find some new structures (by hand) with lower energies.
> The energy difference, ~100 meV, is strongly higher than the accuracy of energy in my calculations; and also the structures are very different.
> In my calculation, the vacuum is large enough and forc_conv_thr is 1.0D-5.
> My question is how can I find the lowest energy structure?
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