Dear Ari
The NEB is not exactly "stuck"
path length = 8.546 bohr
path length = 9.216 bohr
path length = 9.904 bohr
The MEP length keeps increasing. Maybe a look into the trajectory
files can tell you what's happening. If any other source of
misbehavior can be excluded, try to go ahead (maybe fixing the
position of "useless" atoms). I've experienced NEB in large systems
converged after several hundreds steps.
HTH
Giuseppe
Quoting Ari P Seitsonen <[email protected]>:
Dear Users,
I have a problem in the calculations with the method NEB: The
atoms do not get relaxed even if there are clearly forces on the
atoms. The electronic structure converges well, and the relaxation
of the ions follows nicely when the NEB is not used.
I have in the input
BEGIN
BEGIN_PATH_INPUT
&PATH
restart_mode = 'restart'
string_method = 'neb'
nstep_path = 30
ds = 0.2
opt_scheme = "broyden"
num_of_images = 8
k_max = 0.3
k_min = 0.2
CI_scheme = "auto"
! minimum_image = .true.
first_last_opt = .true.
path_thr = 0.1
/
END_PATH_INPUT
and
&ions
/
I have tried with different values of 'num_of_images', 'k_min' and
'k_max', with the climbing image and without. One calculation - a
diffusion path of one ad-atom on a surface - worked well, all other
become stuck with the output like:
------------------------------ iteration 12
------------------------------
cpu = 0 tcpu = 9589.5 self-consistency for image 1
cpu = 0 tcpu = 9656.9 self-consistency for image 3
cpu = 0 tcpu = 9823.9 self-consistency for image 5
cpu = 0 tcpu = 10043.8 self-consistency for image 7
activation energy (->) = 10.012055 eV
activation energy (<-) = 6.833374 eV
image energy (eV) error (eV/A) frozen
1 -78491.5920678 0.000987 F
2 -78490.3334035 7.018378 F
3 -78486.4101831 18.058881 F
4 -78481.6171805 29.752151 F
5 -78481.5800131 29.996389 F
6 -78485.0169815 13.489042 F
7 -78487.7020649 7.675245 F
8 -78488.4133872 8.072137 F
climbing image = 5
path length = 8.546 bohr
inter-image distance = 1.221 bohr
------------------------------ iteration 13
------------------------------
cpu = 0 tcpu = 10165.0 self-consistency for image 1
cpu = 0 tcpu = 10267.1 self-consistency for image 3
cpu = 0 tcpu = 10487.8 self-consistency for image 5
cpu = 0 tcpu = 10710.2 self-consistency for image 7
activation energy (->) = 10.011390 eV
activation energy (<-) = 6.833374 eV
image energy (eV) error (eV/A) frozen
1 -78491.5914028 0.000493 F
2 -78490.3334036 7.099250 F
3 -78486.4101837 17.820470 F
4 -78481.6171812 29.761356 F
5 -78481.5800130 29.998875 F
6 -78485.0169810 13.636010 F
7 -78487.7020648 7.675132 F
8 -78488.4133870 8.071850 F
climbing image = 5
path length = 9.216 bohr
inter-image distance = 1.317 bohr
------------------------------ iteration 14
------------------------------
cpu = 0 tcpu = 10843.3 self-consistency for image 1
cpu = 0 tcpu = 10962.6 self-consistency for image 3
cpu = 0 tcpu = 11183.6 self-consistency for image 5
cpu = 0 tcpu = 11420.4 self-consistency for image 7
activation energy (->) = 10.011390 eV
activation energy (<-) = 6.833374 eV
image energy (eV) error (eV/A) frozen
1 -78491.5914032 0.000582 F
2 -78490.3334034 7.139704 F
3 -78486.4101836 17.548234 F
4 -78481.6171812 29.769083 F
5 -78481.5800132 29.998295 F
6 -78485.0169814 13.849319 F
7 -78487.7020642 7.669197 F
8 -78488.4133871 8.072137 F
climbing image = 5
path length = 9.904 bohr
inter-image distance = 1.415 bohr
------------------------------ iteration 15
------------------------------
...
So the atoms do not move, the electronic structure is converged in
few iterations, but the energies of individual images change in the
micro-eVs.
Any idea would be appreciated; thank you in advance for any hints.
Greetings,
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari Paavo Seitsonen / [email protected] / http://www.iki.fi/~apsi/
Слава Україні
GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
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E-mail: <[email protected]>
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