| 9:55:06 PM PST - Tue, Nov 28th 2017 |
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Hello.
I'm trying to do DFT geometry optimization with fluorine-rich molecule, in negatively charged(-1) state.
But every time I run geometry optimization, somehow one of the fluorine falls out from the structure.
(I've tried several initial geometry, roughly optimized with MD, but didn't helped much)
After optimization, distance between the fallen out fluorine and the nearest carbon is approximately 2 aungstrom
This seems very unrealistic to me considering usual C-F bond is around 1.3~1.4 aungstrom
At this moment, I think I should run geometry optimization with a constraint, fixing bond-length of that troublesome C-F.
I checked the documentation and wrote script as below, but constraint didn't work and the troublesome fluorine fall out again.
I'd really appreciate if i can get some advices on fixing constraining bond-length script below.
(Note. I tried to fix carbon (Atom no. 4) and make spring-bond with F (Atom no. 15))
Of course, will also extremely appreciate other advices on how to deal with this "falling out" problem...
Thank you in advance!!
Sincerely.
SKIM.
echo
start molecule
title "Title"
charge -1
geometry units angstroms print xyz autosym
--
end
BASIS
* library 6-31+g*
END
DFT
xc b3lyp
ODFT
MULT 2
DIRECT
NOIO
CONVERGENCE rabuck
MAXITER 1000
END
MEMORY 100000 mb
DRIVER
MAXITER 1000
END
CONSTRAINTS fixf
fix atom 4
spring bond 4 15 50 13.8
END
task dft optimize
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