This question has split into multiple questions.
I will rephrase and repost part of your question later.
I will answer some of your questions here.
I am too busy to reply to any more questions on this topic, but I hope
I helped you.
And in the model-2, there are 4 types of atoms, type-1 is group-DLC,
type-2 is group-sub,
type-3 is group-boundary, type-4 is group-ball
In the model-1, there are 3 types of atoms, type-1 is group-DLC, type-2 is
type-3 is group-boundary.
in the model-2, the pair_style & pair_coeff commands is showed below,
and i have using them in LAMMPS,
pair_style hybrid tersoff morse 4
pair_coeff * * tersoff SiC_1994.tersoff C C C C
pair_coeff 1 2 morse 3.68 1.165 3.25
pair_coeff 2 4 morse 3.68 1.165 3.25
pair_coeff 1 4 morse 3.68 1.165 3.25
But there has some problem in the model-2, in the second step during the
the group-DLC depart form the group-sub, and in the end of the
simulation, the distance
of the group-DLC and group-sub is about 2 Å。 But in the first step of the
simulation, there no
gap between the group-DLC and group-sub. And in the model-1, there no gap
between the group-DLC
I do not know why this happened.
When there are physical problems with the model, I always have the
Are you sure your morse energy parameters are correct?
If these are in units of kJ/mole, the numbers seem small to me.
Your "D0" energy in your morse potential is 3.68. Are these in
kCal/mole? ("units real")?
I ask because typical carbon-bond dissociation energies are over 356
Also: Have you tried visualizing your dump file?
(Run a short simulation and save frequently.)
If you can create a LAMMPS DATA file for your system (you can use
restart2data), then you can use VMD to visualize your trajectory. I
have attached a README file containing some general instructions for
that is why i use the pair_style hybrid tersoff morse in the model-2, but
there is gap between
the group-DLC and group-sub.
Did I misunderstanding the command 'compute group/group' ?
I don't know. Good question. I'll post this question separately.
Sorry, I can not understand the relationship the force and the command
in the model-2, between the group-DLC and group-sub,I will read the manual
understand the 'fix deform' and 'fix move' .
Yes, I want to know the shear and tensile interfacial strength at the boundary
between the group-DLC and group-sub.
I looked up the definition of "interfacial strength" using google.
If I need to use google to try to answer your question, then perhaps I
should let someone more knowledgeable answer it.
According to the web pages I found using google, the "interfacial
strength" is proportional to the area under the "stress-strain" curve
during fracture. Is this what you are trying to do? Are you trying
to break your system and measure the force? If this is not what you
are doing, then please ignore my previous email.
If you are trying to break your system, then you can use "fix move" or
"fix deform", to pull the atoms apart. These fixes can hold on to the
atoms at the top and bottom of your simulation box and force them to
move (to break the system). As this is happening, you can estimate
the stress by calculating the total force on atoms at the top and
bottom as a function. You can do this using the dump command. You do
not have to use "compute group/group".
>If so, then to calculate the force acting on a group of atoms, you can
>save them in your dump file by including fx fy fz in the list of
>arguments to the "dump" command and read them later. You could do
>this, for example using:
>dump 1 all custom 500 DUMP_FILE id type x y z ix iy iz fx fy fz
>This works even if you are using pair_style tersoff.
>Then after your simulation, you would have to write a script to read
>this file and sum these forces over the two groups of atoms to
>calculate the total force on each group. (Perhaps pizza.py can help
>you do this.)
I would try to do what you have advised.
And thanks for you help so careful and kind
Your welcome. I hope I did not lead you astray.
README_visualize.txt (2.85 KB)