[QE-users] [QE-users-NEB] how to load energy and force for initial and final states from PW before NEB calculation

[Thanh Ngoc Pham]

Dear QE-users,


I am currently use NEB to study reaction path.

My question is how to load energy and force for initial and final states 
from PW calculations before we do NEB calculation.

Say, initial and final states are estimated by pw.x separately,

and those energies and forces should be loaded before we do the path 
interpolation and relaxation using neb.x.


The way I run NEB is follow.

I optimize the initial and final images and use it to make input of 
neb.x  as

BEGIN
BEGIN_PATH_INPUT
&PATH
     string_method  = "neb"
     opt_scheme     = "broyden"
     ci_scheme      = "no-CI"
     nstep_path     =  250
     path_thr       =  0.1
     ds             =  1.0
     k_max          =  0.6
     k_min          =  0.4
!    num_of_images  =  2
!restart_mode = "restart"
     num_of_images  =  5
/
END_PATH_INPUT

BEGIN_ENGINE_INPUT
&CONTROL
     pseudo_dir = './'
/

&SYSTEM
     ibrav       =  4
     a           =  5.71
     c           =  20.0
     ntyp        =  2
     nat         =  5
     ecutwfc     =  25.0
     ecutrho     =  100.0
     occupations = "smearing"
     smearing    = "gaussian"
     degauss     =  0.01
/

&ELECTRONS
     conv_thr = 1.0E-6
/

K_POINTS {automatic}
  2  2  1  0 0 0

ATOMIC_SPECIES
Al     26.98154  Al.pbe-rrkj.UPF
H       1.00794  H.pbe-rrkjus.UPF

BEGIN_POSITIONS
FIRST_IMAGE
ATOMIC_POSITIONS {angstrom}
Al      1.427977   0.824443  10.000000  0 0 0
Al      4.283932   0.824443  10.000000  0 0 0
Al      0.000000   3.297772  10.000000  0 0 0
Al      2.855955   3.297772  10.000000  0 0 0
H       1.299617   2.399220  10.000000
LAST_IMAGE
ATOMIC_POSITIONS {angstrom}
Al      1.427977   0.824443  10.000000  0 0 0
Al      4.283932   0.824443  10.000000  0 0 0
Al      0.000000   3.297772  10.000000  0 0 0
Al      2.855955   3.297772  10.000000  0 0 0
H       2.855955   1.500668  10.000000
END_POSITIONS

END_ENGINE_INPUT
END


NEB command is

mpirun -np 36  ./neb.x -nimage 3 -nk 1  -ndiag 1   -i  neb_1.in >  neb_1.out


At the first NEB calculations, 5 scf calculations are formed including 
initial and final images and three intermediates with three image 
parallelization .

It would be nice if I can loaded the energy and force from previous PW 
calculations for initial and final images

so that three scf calculations are done for three intermediates at the 
first step.

Please help me with this problem.


With best regards,

Thanh