No. This is a huge E-difference which must come from something very severe. Did you compare the distances in the 2 case.outputnn file or compare the structures in xcrysden.

On 12/01/2015 07:37 AM, Bruno Landeros wrote:
Dear Peter:

Yes, my mistake. First energy (no symmetry) is
-5752.55335845 Ry.
while second energy is
-5752.17735109 Ry.

Since cell parameters are note small (12.994513, 25.002400, 17.381701 Bohr)
and I was testing convergence I asked for just 1 K point in both cases.
May be this the origin of the discrepancy?

Greetings,

Bruno


Enviado desde Correo de Windows

*De:* pbl...@theochem.tuwien.ac.at <mailto:pbl...@theochem.tuwien.ac.at>
*Enviado el:* ‎martes‎, ‎1‎ de ‎diciembre‎ de ‎2015 ‎12‎:‎16‎ ‎a. m.
*Para:* wien@zeus.theochem.tuwien.ac.at
<mailto:wien@zeus.theochem.tuwien.ac.at>

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.
 >
 >
 > Greetings,
 >
 > Bruno L
 >
 >
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 >

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