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[Purnaansh P Gunaicha <purnaanshg@gmail.com>]

Hi Forum,

 

I did a total energy run for diamond structure of silicon. It gave me an answer. But when i tried to do a similar run by increasing the number of atoms then instead of doubling the energy it gave me an answer which was ten time bigger then the first run. Down are the input files for the runs. Kindly go through them and provide corrections.

 

2atom_diamond structure of silicon

 

Input

 

acell  10.18 10.18 10.18
rprim
0.0 0.5 0.5
0.5 0.0 0.5
0.5 0.5 0.0
ntypat 1
znucl 14
natom 2
typat 1 1
xcart
   0.00000000000000 0.00000000000000 0.00000000000000
   0.47243153124000 0.47243153124000 0.47243153124000
ecut  6.0
kptopt 1
ngkpt 8 8 8
nstep 10
toldfe 1.0d-8
diemac 12.0

Output

 

 Components of total free energy (in Hartree) :

    Kinetic energy  =  4.36994139614221E+00
    Hartree energy  =  1.63067519413275E+00
    XC energy       = -4.14284205020298E+00
    Ewald energy    =  5.22656127763713E+00
    PspCore energy  =  8.69853998679169E-02
    Loc. psp. energy= -8.41405033073916E+00
    NL   psp  energy=  4.23463483421105E+00
    >>>>>>>>> Etotal=  2.99190572104891E+00

 Other information on the energy :
    Total energy(eV)=  8.14138950483921E+01 ;

    Band energy (Ha)=  -3.8005471315E-01

 

4atom_diamond structure of silicon

 

Input

 

acell  10.18 10.18 10.18
rprim
0.0 1.0 1.0
0.5 0.0 0.5
0.5 0.5 0.0
ntypat 1
znucl 14
natom 4
typat 1 1 1 1
xcart
   0.00000000000000 0.00000000000000 0.00000000000000
   0.47243153124000 0.47243153124000 0.47243153124000
   0.00000000000000 0.94486306249679 0.94486306249679
   0.47243153124839 1.41729459374519 1.41729459374519
ecut  6.0
kptopt 1
ngkpt 8 8 4
nstep 20
toldfe 1.0d-8
diemac 12.0

Output

 

Components of total free energy (in Hartree) :

    Kinetic energy  =  1.91724843402450E+01
    Hartree energy  =  2.15989723059174E+01
    XC energy       = -1.06573757754708E+01
    Ewald energy    =  5.08787961524851E+01
    PspCore energy  =  1.73970799735834E-01
    Loc. psp. energy= -6.68898326663691E+01
    NL   psp  energy=  1.19449362248025E+01
    >>>>>>>>> Etotal=  2.62219513813459E+01

 Other information on the energy :
    Total energy(eV)=  7.13535584596061E+02 ;

    Band energy (Ha)=  -2.7529499134E+00

Also, the enrgies are positive which does not make sense. Kindly provide the relevant help.

 

Thank you

Purnaansh Gunaicha