[Pw_forum] Lattice Constant Optimization of Aluminum

[Paul M. Grant]

To All:  

(BTW: PG: My last note on the "default" value of npk should have been termed
"default maximum."  Sorry, but we Americans haven't spoken English since
1776.  Anyway, thanks for pointing me to the right Fortran routine.)

I'm trying to do a very simple homework problem with PWscf.the optimization
of the lattice constant of aluminum.

Even with a wildly wrong first estimate of celldm(1) of 7.2 (the
experimental value at RT is 7.665 au), I get zero net individual atomic
forces and thus no optimization.  I've gotten "relax" in PWscf to work with
a lot more complex polymer monoclinic unit cell containing eight atoms and
two different elements.  So, I must be doing something really dumb
(stupid).maybe I should be using vc-relax instead?  Anyway, here's the I/O
(scusi e grazie):

INPUT

&control

    title               = '$prefix_root$s$i.rx.in'

    calculation                 = 'relax'

    restart_mode = 'from_scratch',

    prefix                        = '$prefix_root$s$i',

    pseudo_dir                = '/home/pmpgrant/espresso-3.2/pseudo/',

    outdir                        = '$home_root',

    verbosity                   = 'minimal',

    tprnfor                       = .false.,

    tstress                      = .true.,

 /

 &system

    ibrav              = 2,

    celldm(1)                   = 7.2,

    nat                            = 1, 

    ntyp              = 1,

    ecutwfc                     = 15,

    occupations               = 'smearing',

    smearing                   = 'methfessel-paxton',

    degauss                    = 0.05,

    la2F              = .false., 

 /

 &electrons

    diagonalization           = 'david',

    conv_thr                    = 1.0d-12,

    mixing_beta   = 0.7,

 /

&ions

    ion_dynamics            = 'bfgs',

    pot_extrapolation       = 'second-order',

    wfc_extrapolation       = 'second-order',

/

ATOMIC_SPECIES

 Al  26.98 Al.vbc.UPF

ATOMIC_POSITIONS

 Al 0.00 0.00 0.00 

K_POINTS {automatic}

32 32 32 0 0 0

OUTPUT

The total energy is the sum of the following terms:

 

     one-electron contribution =     3.23304593 Ry

     hartree contribution      =     0.01297127 Ry

     xc contribution           =    -1.69806267 Ry

     ewald contribution        =    -5.73107767 Ry

     smearing contrib. (-TS)   =     0.00011533 Ry

 

     convergence has been achieved

 

     Forces acting on atoms (Ry/au):

 

     atom   1 type  1   force =     0.00000000    0.00000000    0.00000000

 

     Total force =     0.000000     Total SCF correction =     0.000000

     SCF correction compared to forces is too large, reduce conv_thr

 

 

     entering subroutine stress ...

 

          total   stress  (Ry/bohr**3)                   (kbar)     P=
110.51

   0.00075124   0.00000000   0.00000000        110.51      0.00      0.00

   0.00000000   0.00075124   0.00000000          0.00    110.51      0.00

   0.00000000   0.00000000   0.00075124          0.00      0.00    110.51

 

 

     BFGS Geometry Optimization

 

     bfgs converged in   1 scf cycles and   0 bfgs steps

 

     End of BFGS Geometry Optimization

 

     Final energy =      -4.1830078084 Ry

 

CELL_PARAMETERS (alat)

  -0.500000000   0.000000000   0.500000000

   0.000000000   0.500000000   0.500000000

  -0.500000000   0.500000000   0.000000000

 

ATOMIC_POSITIONS (alat)

Al       0.000000000   0.000000000   0.000000000

 

 

Paul M. Grant, PhD

Principal, W2AGZ Technologies

Visiting Scholar, Applied Physics, Stanford University

EPRI Science Fellow (Retired)

IBM Research Staff Member Emeritus

 <mailto:w2agz at pacbell.net> w2agz at pacbell.net

 <http://www.w2agz.com/> http://www.w2agz.com

 

 

 

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