Thank you.
I did not notice the unit difference in pw.x and cp.x.
But it seems that the energies that both codes obtained agree well. I
pasted the results in the following. The first one is the result from
vc-relax operated on one unit cell, the total energy is -358.1 Ry, this is
very close to my original setup with scf calculation. The second one is
from cp.x operated on 2 by 2 by 2 supercell, with fixed atom positions(ion
and cell_dynamics are set to 'none'), the energy is -1410 au==-2820 Ry. I
don't know whether this is a big difference, but I cannot find an obvious
error, but the pressure is quite high, like100GPa, and it is sensitive to
the setup especially $electron part.
I don't quite get your point about the default positions of atoms in pw and
cp. In both codes, I used 'crystal', and in the supercell, all the ratios
are in reference to this cubic supercell. I don't think the atom positions
have much problem from the result.
Thank you!
Tian
---------------------------------------------------------------------------------------------
pw.x
------------------------------------------------------------------------------------------
total energy = -358.09688074 Ry
Harris-Foulkes estimate = -358.09688074 Ry
estimated scf accuracy < 9.1E-14 Ry
The total energy is the sum of the following terms:
one-electron contribution = -98.88874403 Ry
hartree contribution = 94.24811082 Ry
xc contribution = -60.23256770 Ry
ewald contribution = -293.22367983 Ry
convergence has been achieved in 27 iterations
Forces acting on atoms (Ry/au):
atom 1 type 2 force = 0.00000000 0.00000000 0.00000000
atom 2 type 2 force = 0.00000000 0.00000000 -0.00000000
atom 3 type 2 force = 0.00000000 -0.00000000 -0.00000000
atom 4 type 2 force = -0.00000000 0.00000000 -0.00000000
atom 5 type 1 force = 0.00000000 0.00000000 0.00000000
atom 6 type 1 force = 0.00000000 0.00000000 0.00000000
Total force = 0.000000 Total SCF correction = 0.000000
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P=
-0.08
-0.00000054 0.00000000 0.00000000 -0.08 0.00 0.00
0.00000000 -0.00000054 0.00000000 0.00 -0.08 0.00
0.00000000 0.00000000 -0.00000054 0.00 0.00 -0.08
bfgs converged in 5 scf cycles and 2 bfgs steps
(criteria: energy < 0.10E-03, force < 0.10E-02, cell < 0.50E+00)
End of BFGS Geometry Optimization
Final enthalpy = -358.0968807430 Ry
Begin final coordinates
new unit-cell volume = 774.49676 a.u.^3 ( 114.76858 Ang^3 )
CELL_PARAMETERS (alat= 9.15690000)
1.002900997 0.000000000 0.000000000
0.000000000 1.002900997 0.000000000
0.000000000 0.000000000 1.002900997
ATOMIC_POSITIONS (crystal)
Ag 0.250000000 0.250000000 0.250000000
Ag 0.750000000 0.750000000 0.250000000
Ag 0.250000000 0.750000000 0.750000000
Ag 0.750000000 0.250000000 0.750000000
O 0.000000000 0.000000000 0.000000000
O 0.500000000 0.500000000 0.500000000
End final coordinates
------------------------------------------------------------------------------------
cp.x
------------------------------------------------------------------------------------
Partial temperatures (for each ionic specie)
Species Temp (K) Mean Square Displacement (a.u.)
1 0.00 0.0000
2 0.00 0.0000
nfi ekinc temph tempp etot enthal econs
econt vnhh xnhh0 vnhp xnhp0
100 0.00092 0.0 0.0 -1431.80272 -1431.80272 -1431.80272
-1431.80180 0.0000 0.0000 0.0000 0.0000
writing restart file: ./Ag2O_51.save
restart file written in 39.227 sec.
Averaged Physical Quantities
accomulated this run
ekinc : 7.61699 7.61699 (AU)
ekin : 374.63650 374.63650 (AU)
epot : -1373.54937 -1373.54937 (AU)
total energy : -1410.67335 -1410.67335 (AU)
temperature : 0.00000 0.00000 (K )
enthalpy : -1410.67335 -1410.67335 (AU)
econs : -1410.67335 -1410.67335 (AU)
pressure : 93.03124 93.03124 (Gpa)
volume : 6148.60237 6148.60237 (AU)
On Thu, Sep 13, 2012 at 1:22 AM, Paolo Giannozzi <giannozz at
democritos.it>wrote:
> On Wed, 2012-09-12 at 15:33 -0700, Tian Lan wrote:
>
> > I expected a good structure from scf calculation should more or less
> > agree with the MD run.
>
> it does. First of all, you should verify that you can get the same
> energy (within numerical noise, and not forgetting the Ha to Ry
> conversion) with pw.x and cp.x (beware the different defaults
> for atomic positions in input). In the latter case, just perform
> an electronic minimization at fixed atoms.
>
> P.
> --
> Paolo Giannozzi, IOM-Democritos and University of Udine, Italy
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
--
Lan, Tian
Ph.D. Candidate, Department of Applied Physics and Materials Science
California Institute of Technology,
Caltech M/C 138-78, Pasadena, CA, 91125
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