TO THE PROBLEM OF APPLICABILITY OF THE TAMMAN TEMPERATURE CONCEPT TO NANOSIZED OBJECTS: TO THE 160TH ANNIVERSARY OF GUSTAV TAMMAN

Abstract

The introduction provides a brief critical review of the available definitions and interpretations of the Tamman temperature, usually defined as Т(∞)T=0,5T(∞)m, and of the Hüttig temperature Т(∞)H=0,3T(∞)m where T(∞)m is the macroscopic value of the melting point of the material. For a nanoparticle we propose to replace in the above relations T(∞)m by the melting temperature of the small object Tm, i.e. to define TT as 0,5Tm and TH as 0,3Tm. In our molecular dynamics experiments on Au nanoparticles, carried out using the LAMMPS program, we found that at the temperature T=TT, in both the central part of the fcc nanoparticle (the core) and in its surface layer (the shell), some local species of a quasicrystalline structure appear which are alternately identified either as crystalline or as non-crystalline by the OVITO program. However, contrary to opinion of E. Rukenstein (1984), at T=TT, a liquid layer on the surface of the crystalline nanoparticle is not formed yet. However, a liquid-like layer was gradually developed in the course of the further temperature elevation. At the same time, in our molecular dynamics experiments we did not reveal any manifestation of the Hüttig temperature TH in the structure of crystalline Au nanoparticles reproduced in our molecular dynamics experiments. It is also of interest that in our molecular dynamics experiments the nanoparticle sintering took place not only above the Tammann temperature but below it as well.

Keywords

• tamman temperature
• hüttig temperature
• metal nanoparticles
• surface melting
• sintering
• molecular dynamics