[Pw_forum] missing eigenvalue

Paolo Giannozzi giannozz at nest.sns.it
Mon Jun 16 10:53:00 CEST 2003


Hi

> HOMO is non degenerate, the difference in energy between HOMO
. and LUMO is around 0.3 ryd.

eV, not Ry. This is however what you get if you use only Nelec/2 states
for scf, which in this particular case leads to the wrong scf charge density.

You need to add more states in the scf calculation, AND to add a broadening
to the states. If HOMO and LUMO cross during self-consistency, the charge 
density has discontinuous jumps and the scf procedure may not converge. 
The broadening (gaussaina or whatever) smoothes the jump and allows
self-consistency to proceed smoothly to the good ground state.

With the true scf charge density, your system has a 0.1 eV HOMO-LUMO
gap. See attached input and output (for the new version of the code)

Paolo
-------------- next part --------------
 &control
    calculation = 'scf'
    restart_mode='from_scratch',
    tprnfor = .true.
    pseudo_dir = '/home/giannozz/O-sesame/pseudo/',
    outdir='/home/giannozz/tmp/'
 /
 &system
    ibrav=  1, celldm(1) =24.00, nat=  6, ntyp= 1,
    ecutwfc=20.0,
    nbnd = 14, occupations='smearing', smearing='gaussian',
    degauss=0.05
 /
 &electrons
    mixing_mode = 'plain'
    mixing_beta = 0.7 
    conv_thr =  1.0d-8
 /
ATOMIC_SPECIES
 Al  26.98 Al.vbc.UPF
ATOMIC_POSITIONS {alat}
 Al   0.149002977    0.010536102   0.000000000
 Al  -0.149002977   -0.010536102   0.000000000
 Al  .010536102      0.149002977   0.000000000
 Al -.010536102     -0.149002977   0.000000000
 Al   0.000000000    0.000000000   0.149002977
 Al   0.000000000    0.000000000  -0.149002977
K_POINTS {Gamma}
-------------- next part --------------

     Program PWSCF 1.2.1  starts ...
     Today is 16Jun2003 at 10:42:52 

     Ultrasoft (Vanderbilt) Pseudopotentials, Gamma point

     Current dimensions of program pwscf are:
     ntypx = 6   npk =40000  lmax = 3
     nchix = 6  ndim = 2000  nbrx = 8 nqfm = 8


     bravais-lattice index     =            1
     lattice parameter (a_0)   =      24.0000  a.u.
     unit-cell volume          =   13824.0000 (a.u.)^3
     number of atoms/cell      =            6
     number of atomic types    =            1
     kinetic-energy cutoff     =      20.0000  Ry
     charge density cutoff     =      80.0000  Ry
     convergence threshold     =      1.0E-08
     beta                      =       0.7000
     number of iterations used =            8  plain     mixing
     Exchange-correlation      =  SLA  PZ   NOGX NOGC (1100)
     iswitch =  0

     celldm(1)=   24.00000  celldm(2)=    0.00000  celldm(3)=    0.00000
     celldm(4)=    0.00000  celldm(5)=    0.00000  celldm(6)=    0.00000

     crystal axes: (cart. coord. in units of a_0)
               a(1) = (  1.0000  0.0000  0.0000 )  
               a(2) = (  0.0000  1.0000  0.0000 )  
               a(3) = (  0.0000  0.0000  1.0000 )  

     reciprocal axes: (cart. coord. in units 2 pi/a_0)
               b(1) = (  1.0000  0.0000  0.0000 )  
               b(2) = (  0.0000  1.0000  0.0000 )  
               b(3) = (  0.0000  0.0000  1.0000 )  


     PSEUDO 1 is Al         zval =  3.0   lmax= 1   lloc= 0
     (in numerical form:   171 grid points, xmin =  0.00, dx = 0.0000)

     atomic species   valence    mass     pseudopotential
        Al             3.00    26.98000     Al( 1.00)

      8 Sym.Ops. (with inversion)


   Cartesian axes

     site n.     atom                  positions (a_0 units)
         1           Al  tau(  1) = (  0.1490030  0.0105361  0.0000000  )
         2           Al  tau(  2) = ( -0.1490030 -0.0105361  0.0000000  )
         3           Al  tau(  3) = (  0.0105361  0.1490030  0.0000000  )
         4           Al  tau(  4) = ( -0.0105361 -0.1490030  0.0000000  )
         5           Al  tau(  5) = (  0.0000000  0.0000000  0.1490030  )
         6           Al  tau(  6) = (  0.0000000  0.0000000 -0.1490030  )

     number of k points=    1  gaussian broad. (ryd)=  0.0500     ngauss =   0
                       cart. coord. in units 2pi/a_0
        k(   1) = (   0.0000000   0.0000000   0.0000000), wk =   2.0000000

     G cutoff = 1167.2200  (  83519 G-vectors)     FFT grid: ( 72, 72, 72)

     nbndx  =    56  nbnd   =    14  natomwfc =    24  npwx   =   10408
     nelec  =   18.00 nkb   =    24  ngl    =     975

     Initial potential from superposition of free atoms

     starting charge =  17.98766
     Starting wfc are atomic
 

     total cpu time spent up to now is      7.97 secs

     iteration #  1     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  1.00E-02,  avg # of iterations =  3.0

     total energy              =   -24.07499764 ryd
     estimated scf accuracy    <     0.66195088 ryd

     total cpu time spent up to now is     22.32 secs

     iteration #  2     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  3.68E-03,  avg # of iterations =  3.0

     total energy              =   -23.88371294 ryd
     estimated scf accuracy    <     0.96342749 ryd

     total cpu time spent up to now is     37.00 secs

     iteration #  3     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  3.68E-03,  avg # of iterations =  2.0

     total energy              =   -24.43852687 ryd
     estimated scf accuracy    <     0.00104193 ryd

     total cpu time spent up to now is     49.96 secs

     iteration #  4     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  5.79E-06,  avg # of iterations =  4.0

     total energy              =   -24.44004936 ryd
     estimated scf accuracy    <     0.00014695 ryd

     total cpu time spent up to now is     67.04 secs

     iteration #  5     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  8.16E-07,  avg # of iterations =  2.0

     total energy              =   -24.44008319 ryd
     estimated scf accuracy    <     0.00001476 ryd

     total cpu time spent up to now is     80.39 secs

     iteration #  6     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  8.20E-08,  avg # of iterations =  5.0

     total energy              =   -24.44008813 ryd
     estimated scf accuracy    <     0.00000177 ryd

     total cpu time spent up to now is     96.25 secs

     iteration #  7     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  9.81E-09,  avg # of iterations =  5.0

     total energy              =   -24.44008868 ryd
     estimated scf accuracy    <     0.00000027 ryd

     total cpu time spent up to now is    111.44 secs

     iteration #  8     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  1.51E-09,  avg # of iterations =  4.0

     total energy              =   -24.44008880 ryd
     estimated scf accuracy    <     0.00000001 ryd

     total cpu time spent up to now is    125.38 secs

     iteration #  9     ecut=    20.00 ryd     beta=0.70
     Davidson diagonalization with overlap
     ethr =  6.13E-11,  avg # of iterations =  3.0

          k = 0.0000 0.0000 0.0000 (10408 PWs)   bands (ev):

   -11.9006  -8.7303  -8.2956  -7.9044  -5.2864  -5.1763  -4.6844  -4.4611
    -4.1198  -4.0166  -2.6876  -2.5753  -2.4730  -1.2740

     the Fermi energy is    -3.9438 ev

!    total energy              =   -24.44008880 ryd
     estimated scf accuracy    <     0.00000000 ryd

     band energy sum           =    -8.87823805 ryd
     one-electron contribution =   -60.53071604 ryd
     hartree contribution      =    31.30455932 ryd
     xc contribution           =    -8.41306975 ryd
     ewald contribution        =    13.28117646 ryd
     correction for metals     =    -0.08203880 ryd

     convergence has been achieved

     Forces acting on atoms (Ry/au):

     atom   1 type  1   force =     0.00707363   -0.01749475    0.00000000
     atom   2 type  1   force =    -0.00707363    0.01749475    0.00000000
     atom   3 type  1   force =    -0.01749475    0.00707363    0.00000000
     atom   4 type  1   force =     0.01749475   -0.00707363    0.00000000
     atom   5 type  1   force =     0.00000000    0.00000000   -0.00257516
     atom   6 type  1   force =     0.00000000    0.00000000    0.00257516

     Total force =     0.103424     Total SCF correction =     0.000069

     Writing file pwscf.pun     for program phonon
 
     PWSCF        :  2m20.74s CPU time

     init_run     :     7.83s CPU
     electrons    :   131.11s CPU
     forces       :     1.63s CPU
 
     electrons    :   131.11s CPU
     c_bands      :    84.81s CPU (       9 calls,   9.423 s avg)
     sum_band     :    15.35s CPU (       9 calls,   1.705 s avg)
     v_of_rho     :    19.41s CPU (      19 calls,   1.022 s avg)
     mix_rho      :    11.17s CPU (       9 calls,   1.241 s avg)
 
     c_bands      :    84.81s CPU (       9 calls,   9.423 s avg)
     init_us_2    :     1.30s CPU (      19 calls,   0.068 s avg)
     cegterg      :    83.17s CPU (       9 calls,   9.241 s avg)
 
     sum_band     :    15.35s CPU (       9 calls,   1.705 s avg)
 
     wfcrot       :     4.68s CPU
     cegterg      :    83.17s CPU (       9 calls,   9.241 s avg)
     h_psi        :    77.35s CPU (      41 calls,   1.887 s avg)
     g_psi        :     0.60s CPU (      31 calls,   0.019 s avg)
     overlap      :     2.29s CPU (      31 calls,   0.074 s avg)
     cdiaghg      :     0.33s CPU (      32 calls,   0.010 s avg)
     update       :     4.39s CPU (      31 calls,   0.142 s avg)
     last         :     0.88s CPU (       9 calls,   0.098 s avg)
 
     h_psi        :    77.35s CPU (      41 calls,   1.887 s avg)
     init         :     0.49s CPU (      41 calls,   0.012 s avg)
     add_vuspsi   :     3.95s CPU (      41 calls,   0.096 s avg)
 
      General routines
     cft3         :    15.46s CPU (      76 calls,   0.203 s avg)
     cft3s        :    64.82s CPU (     485 calls,   0.134 s avg)
     davcio       :     0.16s CPU (      10 calls,   0.016 s avg)
 


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