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Query about the parameter degaussw 
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Joined: Sat Mar 03, 2018 7:37 am
Posts: 75
University: IIIT Allahabad
Post Query about the parameter degaussw
Dear Experts,
I would like to know the range of degaussw (Smearing in the energy-conserving delta functions). What range of degaussw values should I choose for convergence? It is defined that the default value of degaussw is 0.025 ev. We can't go below the value 0.025 but what is the maximum range of degaussw to obtain converged result? Please let me know.

Thanks and regards,
Anindya Bose
Research Fellow,
IIIT Allahabad

Fri Jun 29, 2018 5:46 am
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Joined: Wed Jan 13, 2016 7:25 pm
Posts: 573
University: Oxford
Post Re: Query about the parameter degaussw
Dear Anindya Bose,

The larger the value of degaussw, the faster you should converged (i.e. the smallest the fine grid required to converged).
On the other hand, it will converge to a "wrong value" (i.e. a value different from the one you would get with true delta functions and infinite sampling).

Therefore there should be an optimum: you should use the largest value possible such that your results do not change too much.

Personally, I always use 0.005 or 0.001 (5 or 1 meV) to be on the accurate side but larger value can be used (some publications used 0.1=100 meV for example. Although recent publication usually use 10 meV).
It also depend on the physical quantities you are looking at as well as your system.

Best wishes,

Dr. Samuel Poncé
Department of Materials
University of Oxford
Parks Road
Oxford OX1 3PH, UK

Fri Jun 29, 2018 2:01 pm
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