I need to model the change in atomic structure in a spatially defines manner. In other words, I cannot assume an infinite crystal and I want to know how the amorphous material will rearrange.
If you have already the material, you can use diffraction methods to model the transition. You can use a combination of the PDF (pair distribution function) approach and of the WPPM (whole powder pattern modelling, that we developed) to model the transition. Each of them has advantages and disadvantages. For the PDF you need a large span in Q (Mo data, synchrotron or neutrons), for WPPM, lab can be sufficient: the PDF is better in the amorphous regime, the WPPM can be more informative in the (nano)crystalline one). I have already modeled the transition from a xerogel to a nanocrystalline powder and found out that the gel was clearly not totally amorphous.
Of course you can use the experimental information on the real material as constraint for molecular dynamics! I think in any case the chances of success mostly depend on the system you are working with and the availability of good potentials...
Hezequiel, sounds interesting: from your data I could easily simulate the expected diffraction pattern...
Sorry Jingzhi, but it is definitely not a new research area!
We are making progress in modeling similar phenomena by hyperdynamics. (Voter). I will let you know whether we get any interesting results
I'm sorry that I don't know there are any available modeling method. This means, it is an new research area. You got unique chance to be No. 1.
it is possible...by rearranging the molecular structure more uniformly and more consistency and proper arrangement of the structure...
I have achieved such transformation through control of variable parameters.....
If you have already the material, you can use diffraction methods to model the transition. You can use a combination of the PDF (pair distribution function) approach and of the WPPM (whole powder pattern modelling, that we developed) to model the transition. Each of them has advantages and disadvantages. For the PDF you need a large span in Q (Mo data, synchrotron or neutrons), for WPPM, lab can be sufficient: the PDF is better in the amorphous regime, the WPPM can be more informative in the (nano)crystalline one). I have already modeled the transition from a xerogel to a nanocrystalline powder and found out that the gel was clearly not totally amorphous.
Of course you can use the experimental information on the real material as constraint for molecular dynamics! I think in any case the chances of success mostly depend on the system you are working with and the availability of good potentials...
Hezequiel, sounds interesting: from your data I could easily simulate the expected diffraction pattern...
Sorry Jingzhi, but it is definitely not a new research area!
I believe that metadynamics is a possible method. See, e.g., D. Quigley and P.M. Rodger 2008. Also, see C. Degranges and J. Delhommelle, 2007.
David Raymand from Uppsala University used the Reax Force Field code to study the thermal annealing and phase transition of ZnO nanoparticles. Here is his PhD thesis: http://uu.diva-portal.org/smash/record.jsf?searchId=1&pid=diva2:343022
I don't know how far they are in this type of study but at least you know that it is possible in that way.
Regards,
Tanguy
You can use free package LAMMPS for molecular dynamics simulation
The transition from an amorphous state to a crystalline state via thermal annealing involves crystal growth where energy comes from the heat energy given to the material. Crystal growth process normally starts with nucleation and on to the crystal growth process itself. In a thermal annealing process, the crystal grows according to the thermodynamics and the equilibrium conditions of the material according to the phase. The heat energy increases the diffusion occurring during the crystal growth process. It has to be decided if the crystal growth process is from a liquid or gas phase to the solid phase. Then one has to start with the proper diffusion equation and if it is for a spatially non-infinite case of nanocrystals, then a suitable boundary condition has to be chosen. (Read B.K. Johnson Phys Rev E (1999); Viswanatha & Sarma, Nanomaterials Chemistry, Wiley)
All of the above answers to your query are superfluous, irrelevalent and do not answer your question in an accurate manner (except mine). Nanoparticles are conglomerates of atoms in which there are no crystal defects, i.e.- delta-S = 0. An amorphous material is glassy. It is well known that if you heat glass beyond its glass transition point, T-sub.g, and its softening point, it will devitrify and form a crystalline product. This can be easily followed by differential thermal analysis - RC Ropp
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures