Coalescence molecular dynamics

G.P. Potimiche et al A molecular dynamics study of void growth and coalescence in single crystal nickel. Int. J. Plasticity 22, 257-278 (2006)... 

Fig. 2.12. Snapshots (top view) from a molecular dynamics simulation of the coalescence of an adsorbed pentamer (ABODE) with a single adatom (F). Reproduced from [207]. Copyright 1999 American Physical Society...

Molecular dynamics (MD) computations of coalescence have been made for silicon nanoparticles ranging in size from. 30 to 480 atoms, corresponding to a maximum diameter smaller than. 3 nm (Zachariah and Cairier, 1999), The compulations were based on an interatomic potential developed for silicon atoms with covalent bonding. The particle structure was assumed to be amorphous. The MD simulations indicate that the transition between solid and liquid-state behavior occurs over a wide temperature range significantly lower than the melting point of bulk silicon (1740 K), a well-known effect for nanoparticics (Chapter 9), The broadest transition occurred for the smallest particles studied (30 atoms), probably becau.se the surface atoms make up a large fraction of the particle mass. 

Figure 12.7 Compiiier. sinnilaiions of coalescence times for particles composed of varying numbers of silicon atoms. The dotted lines connecuhe molecular dynamic compulations based on the approach of the moment of inertia of two coalescing particles in contact to the value for the sphere of (he same volume. The solid lines show calculations ba.scd on the phenomenological theories, (12.3) and (12.6). Values calculated from (12.6) (for the liquid) were multiplied by a factor of 10 on the grounds that viscosity values fur bull silicon are (oo smalt for nanoparticles. (After Zachariah and Carrier. 1099.)...

F. Ding, A. Rosen, K. Bolton, Size dependence of the coalescence and melting of iron clusters a molecular-dynamics study. Phys. Rev. B 70(7), 075416 (2004)... 

NMR in solution and solid phase was used for investigation of molecular dynamics in esters of a-tocopherol. Measuring of coalescence points for broadened resonances of C2a, C3, and Cl carbons (see Figure 49.12) enabled determination of dynamic parameters (k, AG ) of heterocyclic ring. 

Coalescence occurs in shear as well as in quiescent systems. In the latter case the effect can be caused by molecular diffusion to regions of lower free energy, by Brownian motion, dynamics of concentration fluctuation, etc. Diffusion is the mechanism responsible for coalescence known as Ostwald ripening". The process involves diffusion from smaller drops (high interfacial... 

---