[DFTB-Plus-User] Trustworthy of the energy minimization

[한대호]

Hello.

I just started to use DFTB+ program, and I thought that It'd better perform
some simple calculation for the test.

So, I tried to do energy minimization of water(H2O) molecule as the
following example.

http://www.dftb-plus.info/fileadmin/DFTB-Plus/public/recipes/html/basics/firstcalc.html

Then I get the minimized energy of water molecule: -4.0590812857 H

This value is similar to -4.0779379339 H in the example.

However, the known experimental value of the electronic ground state energy
of water molecule is -76.481 H.

http://www.sciencedirect.com/science/article/pii/0009261469800448

I know that the example input is not for the advanced-level calculation,
but the discrepancy so large.

How can I get more accurate minimized energy for water molecule?

Daeho
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