[gpaw-users] Error estimations for different XCs

[Wellendorff, Jess]

Dear Wei,

a much more systematic approach to your quest is to use the BEEF-vdW functional with the corresponding Bayesian Error Estimation Ensemble.
This ensemble actually does exactly what you are looking for without the need for you to specify which "standard functionals" define the spread of DFT results. Instead, the error estimate (or estimate of the spread of predictions by different density functionals) is calculated simply as the square root of the variance over the BEEF-vdW ensemble predictions. Search for "BEEF-vdW" on the GPAW web pages.

I really recommend this approach. It gives you a much less biased and more quantitative estimate of the sensitivity of your DFT result wrt the density functional you have chosen. Think about the inherent bias in this way: How can you be sure that you know by heart the two density functionals that would provide predictions at the two ends of the true distribution of DFT predictions of the quantity you are interested in ??? That is very hard, if not impossible. But the BEE approach offers a convenient and cheap estimate of how much your DFT prediction would change had you chosen other XC functionals than the BEEF-vdW one (provided the quantity of interest is posed in terms of total energies).

Best
Jess Wellendorff

On Sep 9, 2013, at 11:49 PM, Glen Jenness wrote:

Dear Wei,

Off the top of my head you can do something like :

calc = GPAW(....)

potentials = ['PBE', 'LDA', 'PW91']

for xc in potentials:
    calc.set(xc=xc)
    <calculate binding energy here>

This will actually work with most of the ASE calculators.

Glen




On Mon, Sep 9, 2013 at 5:18 PM, wei guo <guoweicyclone at gmail.com<mailto:guoweicyclone at gmail.com>> wrote:
Hi guys,

We are interested in calculate the binding energies using different XC to get a sense how the errors are related to XCs.

To save time, I guess one can start from the relaxed structure and in one calculation obtain all the potential energies of a few XCs.

Is there any function or module in GPAW or ASE for doing this

Thanks.
--
Best wishes
Wei
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--
Dr. Glen Jenness
Schmidt Group/Morgan Group
Department of Chemistry/Materials Science and Engineering (MSAE)
University of Wisconsin - Madison
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Dr. Jess Wellendorff
Postdoctoral Researcher
SUNCAT Center for Interface Science & Catalysis
SLAC National Accelerator Laboratory, U.S.A.
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