[Pw_forum] NEB restart from scratch
paolo paoli100
thesis.outputfiles at gmail.com
Sat Nov 23 19:43:39 CET 2013
Dear all pw users,
I performed neb calculations (espresso-5.0.2) with a 25 Ry cutoff and a 6 6
1 k-points grid.
After reaching convergence, with the error on each image lower than the
selected threshold, I tried to refine my calculations by increasing the
cutoff up to 40 Ry, and by using more k-points (8 8 1 grid).
Converged neb (25 Ry)
------------------------------ iteration 39
------------------------------
cpu = 0 tcpu = 23906.3 self-consistency for image 2
cpu = 0 tcpu = 23978.2 self-consistency for image 4
cpu = 0 tcpu = 24086.9 self-consistency for image 6
cpu = 0 tcpu = 24200.3 self-consistency for image 8
cpu = 0 tcpu = 24308.2 self-consistency for image 10
activation energy (->) = 0.894658 eV
activation energy (<-) = 0.836243 eV
image energy (eV) error (eV/A) frozen
1 -19891.2503277 0.071116 T
2 -19891.2158612 0.049589 F
3 -19891.1523863 0.188484 F
4 -19891.0150938 0.162087 F
5 -19890.9987459 0.191508 F
6 -19890.8817497 0.106483 F
7 -19890.6985072 0.123973 F
8 -19890.4818044 0.093420 F
9 -19890.3556701 0.086773 F
10 -19890.5472740 0.113798 F
11 -19891.1235293 0.166418 F
12 -19891.1919133 0.070926 T
climbing image = 9
path length = 10.335 bohr
inter-image distance = 0.940 bohr
---------------------------------------------------------------------------
neb: convergence achieved in 39 iterations
NEB : 6h39m CPU 6h46m WALL
This run was terminated on: 7:53:22 3Jul2013
=------------------------------------------------------------------------------=
JOB DONE.
=------------------------------------------------------------------------------=
So, I created a new input file with the new values of these parameters
(cutoff and k-points grid), and I copied the atomic coordinates from the
.crd file, of the converged path with 25 Ry and 6 6 1 grid. Then, I ran
neb.x with the restart mode: “from_scratch”. Unfortunately the first
iteration of the new neb simulation, with 40 Ry, showed very large forces.
------------------------------ iteration 1
------------------------------
cpu = 0 tcpu = 6.6 self-consistency for image 1
cpu = 0 tcpu = 281.5 self-consistency for image 2
cpu = 0 tcpu = 559.0 self-consistency for image 4
cpu = 0 tcpu = 832.1 self-consistency for image 6
cpu = 0 tcpu = 1092.8 self-consistency for image 8
cpu = 0 tcpu = 1365.2 self-consistency for image 10
activation energy (->) = 38.645703 eV
activation energy (<-) = 38.552298 eV
image energy (eV) error (eV/A) frozen
1 -19892.5055371 0.008676 T
2 -19892.4796891 0.244186 F
3 -19892.4470814 0.232055 F
4 -19892.3936725 0.309786 F
5 -19892.2598441 0.174595 F
6 -19892.2326900 0.376662 F
7 -19892.1508214 0.237737 F
8 -19891.9033607 0.629380 F
9 -19891.5413520 1.554399 F
10 -19890.5368565 23.555285 F
11 -19853.8598346 268.470304 F
12 -19892.4121325 0.021811 T
climbing image = 11
path length = 11.793 bohr
inter-image distance = 1.072 bohr
I don’t know why so huge forces appeared since my initial path is the
converged path with a 25 Ry cutoff, I think the cutoff may affect forces,
but what about the restart mode “from_scratch”?
So I even tried to run the same inputfile with a 25 Ry cutoff and 6 6 1
k-points grid. Since the initial path is the converged path with 25 Ry and
6 6 1 k-points (copy and paste from .crd file) , my neb calculation should
converge after one iteration, instead I have large forces:
------------------------------ iteration 1 ------------------------------
cpu = 0 tcpu = 3.5 self-consistency for image 1
cpu = 0 tcpu = 268.4 self-consistency for image 2
cpu = 0 tcpu = 522.8 self-consistency for image 4
cpu = 0 tcpu = 773.8 self-consistency for image 6
cpu = 0 tcpu = 1020.3 self-consistency for image 8
cpu = 0 tcpu = 1270.4 self-consistency for image 10
activation energy (->) = 38.753850 eV
activation energy (<-) = 38.695436 eV
image energy (eV) error (eV/A) frozen
1 -19891.2503277 0.071116 T
2 -19891.2304040 0.241051 F
3 -19891.2049038 0.226864 F
4 -19891.1588213 0.318751 F
5 -19891.0267566 0.158294 F
6 -19891.0032580 0.382541 F
7 -19890.9283308 0.232692 F
8 -19890.6852427 0.655155 F
9 -19890.3234875 1.547988 F
10 -19889.3355302 23.552337 F
11 -19852.4964773 269.371205 F
12 -19891.1919133 0.070926 T
climbing image = 11
path length = 11.793 bohr
inter-image distance = 1.072 bohr
Could anyone tell me how QE computes forces at iteration number 1, if the
restart mode is from scratch?
How can I deal with this problem?
Thanks to all,
Luca Dietz
Ph.D. student in Chemical Engineering
Politecnico di Milano, Italy
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