[CPMD-list] Platform-dependent output energies

[Eung-Gun Kim]

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.