[CPMD-list] Platform-dependent output energies

[Juerg Hutter]

Hi

the major source of different energies on different
platforms is the FFT library. Different FFT libraries
allow for different number of real space points.
The number of real space points is important for
the calculation of the XC energy.
Look for the line
 REAL SPACE MESH:                   144          144          144
in the output and compare the numbers.

regards

Juerg Hutter

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 1 635 4491
Physical Chemistry Institute   FAX   : ++41 1 635 6838
University of Zurich           E-mail: hutter at pci.unizh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Fri, 26 Mar 2004, Eung-Gun Kim wrote:

> Dear CPMD Mailing List Subscribers,
>
> I have been running tests on different platforms and am getting different energy
> values on different machines.  The platform-dependent results don’t show when I
> run on the sample input files that came with the code.  With my own input file,
> however, I get values of the total energy as different as by 0.1 Ha upon
> switching the machine.  The discrepancies exist before and after geometry
> optimization.  Some relevant info on my input and installation is as follows:
>
> CP Version: 3.7.2
>
> Tested platforms:
> 1) IBM SP2 (AIX 5.2): xlf; MPICH 1.2.5.2; LAPACK 3.0
> 2) IBM Xeon cluster (RedHat 9.0): PGI Fortran compiler 5.1 (with BLAS and
> LAPACK); MPICH 1.2.5.2
>
> System:
>         Aluminum crystal (2x2x2 cells for a total of 32 atoms)
>
> As you note in my input file below, I didn’t use either k-point sampling or FEMD
> for this metallic system.  Portions from each output file are also attached at
> the end of the input file.
>
> Best regards,
>
> E Kim
>
>
> &CPMD
>   OPTIMIZE GEOMETRY
>   PCG MINIMIZE
>   BFGS
>   LSD
>   EMASS
>     900
>   TIMESTEP
>     5
>   MAXSTEP
>     10000
>   TRAJECTORY SAMPLE
>     10
> &END
>
> &DFT
>   FUNCTIONAL BLYP
> &END
>
> &SYSTEM
>   SYMMETRY
>     1
>   ANGSTROM
>   CELL ABSOLUTE
>     8.1  8.1  8.1  0.0 0.0 0.0
>   CUTOFF
>     70
>   CHARGE
>     0
>   MULTIPLICITY
>     1
> &END
>
> &ATOMS
> *Al_MT_GIA_BLYP.psp  KLEINMAN-BYLANDER  RAGGIO=1.0
>   LMAX=D
>     32
>     0.000000000    0.000000000    0.000000000
>     2.025000000    2.025000000    0.000000000
>     0.000000000    2.025000000    2.025000000
>     2.025000000    0.000000000    2.025000000
>     0.000000000    0.000000000    4.050000000
>     2.025000000    2.025000000    4.050000000
>     0.000000000    2.025000000    6.075000000
>     2.025000000    0.000000000    6.075000000
>     0.000000000    4.050000000    0.000000000
>     2.025000000    6.075000000    0.000000000
>     0.000000000    6.075000000    2.025000000
>     2.025000000    4.050000000    2.025000000
>     0.000000000    4.050000000    4.050000000
>     2.025000000    6.075000000    4.050000000
>     0.000000000    6.075000000    6.075000000
>     2.025000000    4.050000000    6.075000000
>     4.050000000    0.000000000    0.000000000
>     6.075000000    2.025000000    0.000000000
>     4.050000000    2.025000000    2.025000000
>     6.075000000    0.000000000    2.025000000
>     4.050000000    0.000000000    4.050000000
>     6.075000000    2.025000000    4.050000000
>     4.050000000    2.025000000    6.075000000
>     6.075000000    0.000000000    6.075000000
>     4.050000000    4.050000000    0.000000000
>     6.075000000    6.075000000    0.000000000
>     4.050000000    6.075000000    2.025000000
>     6.075000000    4.050000000    2.025000000
>     4.050000000    4.050000000    4.050000000
>     6.075000000    6.075000000    4.050000000
>     4.050000000    6.075000000    6.075000000
>     6.075000000    4.050000000    6.075000000
> &END
>
>
> Output from the SP2 run---------------------------------------------
>
>  (K+E1+L+N+X)           TOTAL ENERGY =          -64.39023857 A.U.
>  (K)                  KINETIC ENERGY =           28.11394543 A.U.
>  (E1=A-S+R)     ELECTROSTATIC ENERGY =          -75.61888788 A.U.
>  (S)                           ESELF =          114.89537676 A.U.
>  (R)                             ESR =            0.00001993 A.U.
>  (L)    LOCAL PSEUDOPOTENTIAL ENERGY =           -5.89039837 A.U.
>  (N)      N-L PSEUDOPOTENTIAL ENERGY =           13.16534369 A.U.
>  (X)     EXCHANGE-CORRELATION ENERGY =          -24.16024144 A.U.
>           GRADIENT CORRECTION ENERGY =           -0.22825193 A.U.
>
>
> Output from the Xeon run--------------------------------------------
>
>  (K+E1+L+N+X)           TOTAL ENERGY =          -64.27276166 A.U.
>  (K)                  KINETIC ENERGY =           28.36257064 A.U.
>  (E1=A-S+R)     ELECTROSTATIC ENERGY =          -76.82637865 A.U.
>  (S)                           ESELF =          114.89537676 A.U.
>  (R)                             ESR =            0.00001993 A.U.
>  (L)    LOCAL PSEUDOPOTENTIAL ENERGY =           -6.46519951 A.U.
>  (N)      N-L PSEUDOPOTENTIAL ENERGY =           14.94091935 A.U.
>  (X)     EXCHANGE-CORRELATION ENERGY =          -24.28467349 A.U.
>           GRADIENT CORRECTION ENERGY =           -0.29067887 A.U.
>
>
>
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