[Pw_forum] Total energy value in QE, strange value.

[mohnish pandey]

Dear Joaquin !
                       First off all I will suggest you to decrease the
charge density cutoff. Normally for Ultrasoft Pseudopotential charge density
cutoff equal to  8-10 times of energy cutoff will suffice. Now check the
stress in and forces in you system. And of course before submitting the
calculation I hope you have visualized the structure. The better thing will
be to do relax or vc-relax calculation to get well converged results instead
of doing scf calculation only, because as you know scf is just one
electronic cycle calculation, it does not care for stress or forces.

On Mon, Aug 23, 2010 at 9:10 PM, joaquin peralta <jperaltac at gmail.com>wrote:

> Dear Forum,
>
> I calculated the energy of a aluminium surface, but the value that i
> obtained using this is 'extremely high'  energy, i obtain the same using
> 4.2.1 and 4.1 version of QE.
>
> My input file is :
> =========================================
> &CONTROL
>    calculation           = 'scf'
>    prefix                = 'al-111-43.5'
>    tprnfor               = .true.
>    wfcdir                = './restore/'
>    pseudo_dir            = '/home/jperalta/pseudo/'
>    outdir                = './restore'
> /
> &SYSTEM
>    ibrav                 =  0
>    celldm(1)             =  1.0
>    nat                   = 21
>    ntyp                  = 1
>    ecutwfc               = 30
>    ecutrho               = 500
>    degauss               = 0.03
>    occupations           = 'smearing'
>    smearing              = 'mv'
>    nspin                 = 2
>    starting_magnetization= 0.1
>    nbnd                  = 300
> /
> &ELECTRONS
>    electron_maxstep      = 300
>    mixing_mode           = 'local-TF'
>    mixing_beta           = 0.3
>    mixing_ndim           = 10
> /
> &IONS
> !   ion_dynamics          = 'bfgs'
> /
> &CELL
> !   cell_dynamics         = 'bfgs'
> !   press                 = 0.0D0
> !   press_conv_thr        = 0.1D0
> /
> ATOMIC_SPECIES
> Al  26.982 Al.pbe-sp-van.UPF
> ATOMIC_POSITIONS (angstrom)
> Al   4.295143   -2.479802   43.5
> Al   5.726858   -3.306403   41.689899
> Al   1.431714   -0.826601   41.689899
> Al   2.863429   -3.306403   41.689899
> Al   4.295143   -0.826601   41.689899
> Al   2.863429   -1.653201   39.351919
> Al   7.158572   -4.133004   39.351919
> Al   5.726858   -1.653201   39.351919
> Al   4.295143   -4.133004   39.351919
> Al   8.590287   -4.959604   37.013940
> Al   4.295143   -2.479802   37.013940
> Al   5.726858   -4.959604   37.013940
> Al   7.158572   -2.479802   37.013940
> Al   5.726858   -3.306403   34.675960
> Al   1.431714   -0.826601   34.675960
> Al   2.863429   -3.306403   34.675960
> Al   4.295143   -0.826601   34.675960
> Al   2.863429   -1.653201   32.337980
> Al   7.158572   -4.133004   32.337980
> Al   5.726858   -1.653201   32.337980
> Al   4.295143   -4.133004   32.337980
> K_POINTS (automatic)
> 6 6 6 0 0 0
> CELL_PARAMETERS {cubic}
> 10.822192        0.000000        0.000000
> 5.411096         -9.372293       0.000000
> 0.000000         0.000000        139.892407
> ================================
>
> i change some electrons parameters in order to improve the convergence. I
> don't know if the enery problem is caused for some special parameter or some
> like that. but in a paper of Sanchez et al (Molecular Physics, 2004, vol
> 102, 1045-1055), the energies are aroung 2 to 20 eV.
>
> And the ouput in my case say :
>
>     the Fermi energy is    -1.8658 ev
>
> !    total energy              =   -3357.65873780 Ry  ---------------> 2K
> eV by atom.
>      Harris-Foulkes estimate   =   -3357.65873669 Ry
>      estimated scf accuracy    <       0.00000057 Ry
>
>      The total energy is the sum of the following terms:
>
>      one-electron contribution = -110140.98098627 Ry
>      hartree contribution      =   54852.05508820 Ry
>      xc contribution           =    -409.97773145 Ry
>      ewald contribution        =   52341.24991020 Ry
>      smearing contrib. (-TS)   =      -0.00501849 Ry
>
>      total magnetization       =     0.00 Bohr mag/cell
>      absolute magnetization    =     0.00 Bohr mag/cell
>
>      convergence has been achieved in  34 iterations
>
>
> Any help i really appreciate it.
>
> Best Regards
> Joaquin Peralta
> Iowa State University.
>
> --
> ----------------------------------------------------
> Group of NanoMaterials
> ----------------------------------------------------
> http://www.gnm.cl
> ----------------------------------------------------
> Joaquín Andrés Peralta Camposano
> ----------------------------------------------------
> http://www.lpmd.cl/jperalta
>
> In a world without frontiers,
> who needs Gates and Win.
>
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>


-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
Y6927262,5th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
+919235721300
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