[lammps-users] How to calculate the effectve volume of the atom?

Hello everybody

The atomic-level stress has been mentioned in many papers (eg. works of Diao JK and Cao AJ). I think the definition of the atom volume is the most crucial.
So I wonder to know how to calculate the effective volume of the atom, which is said difficult in the lammps manual. Does the Voronoi volume make sense?
Is it possible to finish this work by using lammps? Or some other alternative methods?

Any suggestions will be appreciated!

2008-12-04

Hi, yangzy,

Good to know you are in this email list.

Regarding your question, I agree that the atom volume is crucial in calculating the atomic-level stress. I know there is a comprehensive way using voronoi volume to do this by Egami et al. (sorry I can not remember the paper right now). However, I dont think it will make much difference for the results. Actually, someone (E. Rabkin, 2007, Acta Mater. 55, 2085-2099) has done this by tracking the atomic volumes and confirmed that volume variation does not exceed 3%.

In an alternative way, maybe it is still under debate that atomic-level stress is not well defined, you can use atomic strain to characterize the free suface effects. You may want to check this paper for more details: “Sample shape and temperature strongly influence the yield strenght of metallic nanopillars”, A. Cao, E. Ma, Acta Materialia, 56, 4816-4828 (2008).

Best and good luck.

AC