Hello everybody,
After recently attending the QE workshop at Penn State, I have been trying to
use QE to fully optimize organic structures. I did not have any issues trying
to fully optimize oxalic acid (a small organic molecule) and its related
dihydrate. However, I have been trying to get naphthalene and durene (aromatic
hydrocarbons) to run but have had significant issues with decreasing volume
with no vdW correction implemented. Naphthalene has a published 5 K structure,
so any decrease in volume is unphysical, and I regularly see an almost 100
Ang^3 decrease in volume (~30 % decrease).
Here are all of the things I have tried:
Normconserving, US, and PAW pseudo potentials
Increasing the cutoffs to high values (up to 150/1500 Ry)
Varying the number of k-points
Various GGA functionals (PBE, PBESOL, BLYP)
Using coordinates from a 'relax' calculation for 'vc-relax' calculations
Using optimized coordinates to do a 'vc-relax' calculation while holding volume
constant ('cell_dofree=shape'), and then trying a full 'vc-relax' calculation
I am new to PW and QE, so maybe I am doing something simple incorrectly. Any
insight would be greatly appreciated. I am attaching the INPUT, OUTPUT of the
most recent naphthalene BLYP test, and the published CIF files for reference.
Thank you very much in advance,
Michael Ruggiero
Syracuse University Chemistry
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