Monday, February 8, 2016

DFTB3 in GAMESS

I recently did my first DFTB3 calculations in GAMESS.  The process wasn't completely obvious, hence this post.

First I got the parameter files from dftb.org.  You have to fill in and email a registration form to get a login so that might take a few days.  I downloaded the 3ob-3-1 parameter set.

The DFTB3-related input can be found below.  My molecule contains C, N, O, and H atoms.  If there are additional atoms then you need to define additional pairs.  It is OK to specify atom pairs for atoms that are not in the molecule, so the easiest might be to define all relevant pairs once and for all and use it in all input files.

The value for dampex and hubder are found in the README file that is located in the 3ob-3-1 folder I downloaded.  hubder defines parameters for N, C, O, and H - in that order.  It was not clear from the manual what the order should be.  I found the correct order by running the input file without hubder. This run prints out the default hubder values in the order  N, C, O, and H and it turns out that is the order you need to use in the input file.

2016.02.09 Update: Yoshio Nishimoto has told me that the order of the hubder parameters is determined by the order in which they appear in $DATA.  Also using MODIO=31 in $SYSTEM will speed up the calculation.

 $basis gbasis=dftb $END
 $dftb ndftb=3 DAMPXH=.t. dampex=4.0
       hubder(1)=-0.1535,-0.1492,-0.1575,-0.1857 $end
 $dftbsk
 C C "/Applications/gamess/3ob-3-1/C-C.skf"
 C H "/Applications/gamess/3ob-3-1/C-H.skf"
 C N "/Applications/gamess/3ob-3-1/C-N.skf"
 C O "/Applications/gamess/3ob-3-1/C-O.skf"
 H C "/Applications/gamess/3ob-3-1/H-C.skf"
 H H "/Applications/gamess/3ob-3-1/H-H.skf"
 H N "/Applications/gamess/3ob-3-1/H-N.skf"
 H O "/Applications/gamess/3ob-3-1/H-O.skf"
 N C "/Applications/gamess/3ob-3-1/N-C.skf"
 N H "/Applications/gamess/3ob-3-1/N-H.skf"
 N N "/Applications/gamess/3ob-3-1/N-N.skf"
 N O "/Applications/gamess/3ob-3-1/N-O.skf"
 O C "/Applications/gamess/3ob-3-1/O-C.skf"
 O H "/Applications/gamess/3ob-3-1/O-H.skf"
 O N "/Applications/gamess/3ob-3-1/O-N.skf"
 O O "/Applications/gamess/3ob-3-1/O-O.skf"
 $end

I would like to thank +Anders Steen Christensen for his help in figuring this out.


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