some questions about the TAD & MD

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1

Dear all

Thank you for your attention. I have some questions about the TAD method when I simualted with it.

I want to simulate Structural transition of NiMn precipitates during aging an alloy, but when I use TAD, I am getting following errors:

application called MPI_Abort(MPI_COMM_WORLD, 1) - process 2

application called MPI_Abort(MPI_COMM_WORLD, 1) - process 0

application called MPI_Abort(MPI_COMM_WORLD, 1) - process 1

when I reset the parameters of NEB, I don`t find any changing in the process of simulation, and I get the same errors again!

I want to know whether the TAD is effective method for this work, and how can I solve this problem?

Here is my in.file

events occur when a neighboring atom diffuses to the vacant site

run this on multiple partitions as

mpirun -np 8 lmp_openmpi -partition 8x1 -in FeNiMo.in

Fe-Ni-Mo solid solution ageing by temperature accelerated dynamics

neighbor 2.0 bin
neigh_modify every 20 delay 0 check no
lattice bcc 2.28
read_restart solidsol2.data

applying force field

pair_style eam/alloy
pair_coeff * * FeNiMo.eam.alloy Fe Ni Mo
group Fe type 1
group Ni type 2
group Mo type 3
group NiMo type 2 3

Temprature accelerated dynamics

compute 1 all msd
compute 2 all event/displace 3.46
fix 1 all nvt temp 2000.0 2000.0 0.01

tad 2000 50 1450 2000 0.05 1.0 2 &
min 1.0e-5 1.0e-5 100 100 &
neb 0.0 0.01 200 200 20 &
min_style cg &
neb_style fire &
neb_log log.neb

tad nsteps nevent tlo thi delta_conf tmax compute

[min etol ftol niter neval]

[neb etol_neb ftol_neb n1steps n2steps nevery]

[min_style min_style]

[neb_style min_style]

[neb_log logfile]

output

dump id all atom 100 project3.lammpstrj
thermo_style custom step temp pe etotal c_1[4]
thermo 100
thermo_modify lost warn
run 10000

I hope to be able to give me some suggestions for solving this problem,

Many Thanks

2

You probably have bad dynamics in one or more of your replicas.
Did you check the log files or screen output files for the individual
replicas to see if their are any error messages, or bad thermodynamic
output?

Steve

3

Hello,
I checked the screen output files and I found following-error:

"Cannot use TAD with atom_modify sort enabled for NEB "

when I reset the parameters of NEB or atom_modify, I dont find any changing in the process of simulation, and I get the same errors again!!! I dont have enough information about the parameters of TAD and I don`t know, how can I reset these parameters?
Would you mind introducing me some sources about TAD to get more informations?

best regards

4

The error message means what it says, and the atom_modify
doc page explains how to turn sorting off. I presume
if you do that, you don't get that error?

The tad doc page has citations to papers about TAD.

Steve

5

Hello,
Many thanks for your emails and considering my requests, I could solve the errors of my project.
I studied the TAD papers in the past, but I didnt understand [ how can I reset these parameters]? by my above question I mean, I cant get the exact meaning of "

6

The tad doc page in LAMMPS explains the meaning of all
the params that LAMMPS uses for TAD - I don't know
what else to tell you. There is also an example script in
examples/tad.

Steve

7

Hello
I want to compute curve of Energy- Diamond(E-r) but I don`t have diamond for
per-atom!!!
How can I do it?
Many kind regards

8

Dear all
I need to parameters of EAM for compile BCC Iron potential,
Would you mind give me parameters of BCC Iron potenial?

Many kind regards
Mohammadi

9

Dear all
I need to EAM code for compile BCC Iron potential,
Would you mind give me this parameters or complete Fe(bcc)NiMo potential ?

Many kind regards
Mohammadi

10

Hello
I want to compute curve of Energy- Diamond(E-r) but I don`t have diamond for
per-atom!!!
How can I do it?

can you please translate your question into
something that people can understand?
this reads like it is encoded.

axel.

11

Dear all
I need to EAM code for compile BCC Iron potential,
Would you mind give me this parameters or complete Fe(bcc)NiMo potential ?

from the documentation of the EAM pair style:

There are several WWW sites that distribute and document EAM
potentials stored in DYNAMO or other formats:

http://cst-www.nrl.navy.mil/ccm6/ap
http://enpub.fulton.asu.edu/cms/potentials/main/main.htm

please kindly help yourself.

axel.

12

And note that EAM for bcc materials is often not
a good match. You may need something more like MEAM
with angular terms.

Steve

13

I think he wants to calculate the Equation of state (EOS) at T=0 K ?

A salute
Oscar G.

14

Dear all
I need to EAM code for compile BCC Iron potential, Please see attached file!
Would you mind give me this parameters or complete Fe(bcc)NiMo potential ?

Many kind regards
Mohammadi

EAM parameters for BCC Iron.docx (13.3 KB)

15

I don't have them. I don't know if they exist. I suggest you check
the WWW sites listed on the LAMMPS eam doc page where they
archive many EAM potentials.

Steve

16

Dear all

Thank you for your attention.

I want to simulate fracture bihavior of bcc alloys , but when I use fix NVT for relaxation system, I am getting following total temperature:

T=1.#QNAN
17

In metal units a fix nvt damping constant of 100 means
100 psec, which is 1 million timesteps. You’re runing
for 10 timesteps, which means the thermostat
will do virtually nothing on that timescale.

Steve

18

more importantly, it looks like you are creating atoms on top of each
other, which should be the origin for getting the infinitely high
energy.

axel.

19

I used shorter damping constant(0.0005) and run 5000 timesteps but I am getting same temperature( T=1.#QNAN)!!!

How should I solve this problem?

Many kind regards

20

Have you tried damping constants in between 0.0005 and 100, which
is 6 orders of magnitude different? 0.0005 is half a timestep, which
makes no sense. Please read the fix nvt doc page and its discussion
of the damping constant.

Steve