The energies you posted are identical !

Anyway: I hope you did not just copy the case.klist file from the low to the high-symmetry case ??

Otherwise: send me your 2 struct files together with the description of the chosen calculational parameters (everything which is non-default) to my private email.

Am 01.12.2015 um 03:00 schrieb Bruno Landeros:
I'm studying a molecular crystal in which two different molecules form
an 1:1 adduct. There are 2 molecules of each kind (4 in total) in the
unit cell. There are 19 atoms in the asymmetric unit, and since it
belongs to the P21/c spacegroup, a total of 76 atoms are contained in
the unit cell. I was trying to find a possible mistake when calculating
interaction energies and I found the next problem:

If I calculate the SCF by manually inserting the 76 positions and giving
it a P1 symmetry the energy converged to
-5752.17735109 Ry.

If I calculate the SCF by inserting the 19 atoms of the asymmetric unit
with the correct symmetry and let the program to generate the rest of
the positions (which where exactly the same as when inserted manually),
the same functional,  same RMT, same K points and same convergence
criteria the energy converged to
-5752.17735109 Ry.

Transforming the energy difference between the 2 calculations gives 195
kcal/mol. The same happened when doing the same for other systems.

My question is, ┬┐shouldn't I get the same energy in both calculations
since it's the same system, same coordinates and the input was prepared
equally except for the symmetry?
Since I'm trying to calculate interaction energies using different
subsystems, some with and some without symmetry, this is a relevant
question to my research.


Bruno L

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