[CPMD-list] Convergence problems

[Eyvaz Isaev]

Dear all,

I am very sorry, but the problems mentioned in my
previous mail remain.I used Ultrasoft pseudopotential
which gave very good lattice parameter using another
planewave code. A unit sell contained 16 Fe atoms.
(2x2x2 cubic cell with 2 atoms in each elemental cub).
The cutoff energy is 30Ry which is usual choice for US
PsP. No k-points (only \Gamma-point) are applied due
to the use of US PsP.

First, one can see that the total energy via lattice
parameter dependence is very starange: there is a
local minimum and then the total energy is diminished
continuosly.

5.68 (F+E2+X-V+O) TOTAL ENERGY = -2167.79293897 A.U.
5.70 (F+E2+X-V+O) TOTAL ENERGY = -2173.13050923 A.U.
5.72 (F+E2+X-V+O) TOTAL ENERGY = -2174.11302057 A.U.
5.74 (F+E2+X-V+O) TOTAL ENERGY = -2151.12462764 A.U.
5.76 (F+E2+X-V+O) TOTAL ENERGY = -2187.28453244 A.U.
5.78 (F+E2+X-V+O) TOTAL ENERGY = -2188.12065715 A.U.
5.80 (F+E2+X-V+O) TOTAL ENERGY = -2188.93486520 A.U.
5.82 (F+E2+X-V+O) TOTAL ENERGY = -2189.74694585 A.U.


Second, something very strange happend after 18th
iteration and ETOT(19) is completley different.
Besides despite DRHOMAX is diminished DETOT change is
abnormal. And at this stage CPMD finished iteration
loops, guessing that a convergence is reached.

 ==     NFI=     16      ETOT=  -1778.209352   TCPU=  
  42.75 ==
 ==     NFI=     17      ETOT=  -1778.219279   TCPU=  
  39.60 ==
 ==     NFI=     18      ETOT=  -1778.218160   TCPU=  
  33.97 ==
 ==     NFI=     19      ETOT=  -2151.124628   TCPU=  
  61.49 ==

 == DRHOMAX= 2.751E-03  DETOT=     2.762E-03    THL=
1.021E-01 ==
 == DRHOMAX= 1.766E-03  DETOT=    -9.927E-03   
THL=-4.123E-01 ==
 == DRHOMAX= 1.720E-03  DETOT=     1.119E-03   
THL=-1.902E+00 ==
 == DRHOMAX= 8.869E-04  DETOT=    -3.729E+02   
THL=-1.922E-01 ==

Third, I have not changed the lattice type which
remains O_h according to CPMD report, but there is no
magnetic moment  found and Fe becomes  paramagnetic.

 TOTAL INTEGRATED SPIN DENSITY              0.000001
 TOTAL INTEGRATED SPIN DENSITY              0.000001

Could you please let me know what is wrong in my input
file? Any comments are appreciated.

Regards,
Eyvaz.

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