Hi everyone,
I intend to build a confined shear model in LAMMPS with the upper and lower walls are Fe2O3. I have constructed the configuration for these wall, but I meet a trouble in applying potential file for Fe2O3. I was known that it is possible to apply Lenard-Jones potential for the interaction between Fe-Fe, Fe-O, O-O, but it will be more perfect if I apply the written potential files such as EAM/EAM_fs… for Fe2O3 as same as the way for applying EAM or EAM_fs for pure Fe model.
Can anybody show me where can I get the potential files for Fe2O3 ?
If you have any LAMMPS examples or tutorials related to Fe2O3, can you share it to me ?
I highly appreciated your helps !
Best regards,
Dinh Thi Ta
Dinh Thi Ta
Ph.D Candidate
School of Mechanical, Materials & Mechatronic Engineering
University of Wollongong
NSW 2522, Australia
I intend to build a confined shear model in LAMMPS with the upper and lower
walls are Fe2O3. I have constructed the configuration for these wall, but I
meet a trouble in applying potential file for Fe2O3. I was known that it is
possible to apply Lenard-Jones potential for the interaction between Fe-Fe,
Fe-O, O-O, but it will be more perfect if I apply the written potential
files such as EAM/EAM_fs... for Fe2O3 as same as the way for applying EAM or
EAM_fs for pure Fe model.
Can anybody show me where can I get the potential files for Fe2O3 ?
the documentation of the eam pair style lists several repositories: http://lammps.sandia.gov/doc/pair_eam.html
if you look around you will see that LAMMPS supports different
formats/variants of EAM potential files.
If you have any LAMMPS examples or tutorials related to Fe2O3, can you share
it to me ?
before going this route, i would recommend to first do survey of the
available literature on MD simulation studes of Fe2O3 and take note
what kind of approaches/potentials people were using (and how
successful they were). i am not an expert in this area of research,
but i vaguely remember, that EAM is good for metals while metal oxides
are quite different animals and thus are likely to require a different
kind of model to be well represented.
Dinh,
If you intend to confine "stuff" between those walls you should also
worry about the stuff-wall interactions as much as how to model the
Fe2O3 system. I don't think using pure LJ interactions for your oxide
would be good enough as LJ potentials tend to render relatively
brittle solids. Again, set the priorities based on the phenomenon that
may be more relevant to your study and then build up from there.
Carlos
Dear Carlos & Akohlmey,
I am grateful for your advices !
I have been reading a few articles related to Fe2O3 in thin film lubrication with alkanes, dodecane, and even many types of polymer. But a few authors implemented spring interaction model in which each surface atom was initially connected by unbreakable harmonic bonds to all neighbouring, other authors implemented COMPASS to apply force field for Fe2O3 in Material Studio(MS) and run this model in MS. I had visited
NIST website and looked at LAMMPS's potential library to find potential file for Fe2O3, but just Fe_EAM, Fe_EAM/fs, or Fe_alloy potential files available at there.
Is there no available written potential file for Fe2O3 in LAMMPS ?
About the "stuff" which Mr Carlos recommended, alkanes or polymers will be implemented as the lubricant. And the interaction between lubricant's atoms and lubricant-solid wall will be described by L-J cut-off interactions.
If I have any misunderstanding, please, let me know !
Best regards,
Dinh Thi Ta
Ph.D Candidate
School of Mechanical, Materials & Mechatronic Engineering
University of Wollongong
NSW 2522, Australia
Phone : (+61) 405 234 812
Email: [email protected]...
Dear Carlos & Akohlmey,
I am grateful for your advices !
I have been reading a few articles related to Fe2O3 in thin film lubrication with alkanes, dodecane, and even many types of polymer. But a few authors implemented spring interaction model in which each surface atom was initially connected by unbreakable harmonic bonds to all neighbouring, other authors implemented COMPASS to apply force field for Fe2O3 in Material Studio(MS) and run this model in MS.
That's because those authors were probably interested in the effects
triggered by the geometry of the solid surfaces on the layering of the
alkane/polymer molecules when considering the confinement of thin
films. What you have to ask yourself is what is the special
property/condition you intend to compute/simulate that justifies
modelling the Fe2O3 system using a EAM potential? Do you intend to
simulate rough surfaces undergoing plastic deformation as a result of
compressing and shearing the system? For the alkane-alkane
interactions the OPLS FF is probably good enough as long as the
applied pressure on the walls is not huge. Not sure for other kind of
polymer as you don't really specify your potential polymeric systems.
If your polymers have non-saturated Carbon bonds then extra care is
needed and chances are you'll have to parametrize the polymer-wall
interactions from scratch. See for example this paper:
Model. Simul. Mater. Sc. Eng.18, 034004 (2010);
doi:10.1088/0965-0393/18/3/034004
Anyways, the more realistic your system gets the more things you'll
have to keep under control. Read the lit very carefully because there
are people who have worked on this field for a long time and have
encountered and published on the many pitfalls to fall into when
modelling thin film lubrication. Anyways, I leave it here as you
didn't really have a LAMMPS Q beyond the potential file for Fe2O3.
Carlos
Hi Carlos,
Many thanks for your quick reply !
I intend to investigate the plastic deformation of monoasperity surfaces of Fe2O3 walls under extreme confined shear conditions by using LAMMPS simulation & calculation. The main aspects I want to concentrate on that are mechanic properties of Fe2O3 surfaces such as friction forces, plastic deformation, temperature profile under lubricating of PEO-PPO-PEO polymer chains. Besides, I also want to observe the adsorption of polymer on Fe2O3 surfaces, and bridging molecules of polymer. For polymer, as I recommended before, I will use "united atoms" to describe CH2, -CH3... groups, and the bond/non-bond interactions for polymer-polymer, polymer-Fe2O3 will be described by L-J cut-off potential. I will think about OPLS FF which you recommended to me. As your advices, it is not good if I use L-J potential for investigation plastic deformation of asperities, so I am finding potential file which integrated to LAMMPS to apply for my model.
One more again, thank you for your advices and helpful documents !
Kind regards,
Dinh Thi Ta
Ph.D Candidate
School of Mechanical, Materials & Mechatronic Engineering
University of Wollongong
NSW 2522, Australia
Phone : (+61) 405 234 812
Email: [email protected]...