S.L. Gafner, L.V. Redel, J.J. Gafner
On the basis of our researches on studying of a thermal capacity ideal copper and nickel fcc cluster with a diameter to 6 nanometers the assumption has been come out, that thermal properties of nanomaterial should depend on degree of particles agglomeration. That is surfaces and interphase borders connected nanoclusters can render strong influence. For hypothesis check were are taken nickel and copper cluster of the various size (4000 7200 atoms) received at modeling of process of synthesis from a gas phase.
In case of great temperatures it was not possible to estimate adequately a role of interphase borders at thermal capacity of nanoparticles. The reason was mass diffusion of atoms Ni or Cu for the purpose of giving real clusters energetically more favorable form and structure. At low temperatures the thermal capacity real clusters has exceeded a thermal capacity of clusters with the ideal form and structure on size from 3.2 % to 10.6 %. Such distinction in a thermal capacity cannot be connected with distinction among surface atoms and atoms belonging to interphase borders. Atoms of that and other grade have coordination number less than 12 and consequently at the analysis spent by us were considered in common. The obtained data give about identical percent of such atoms. Hence, their presence cannot cause various values of a thermal capacity of real clusters at low temperatures. More plausible the assumption that cluster, having the greatest distinction in a thermal capacity in relation to ideal nanoparticles was simultaneously and greatest in space cluster. Possibly, big linear length of clusters gives the chance to prove its low-frequency part of phonon spectrum, reducing average frequency of fluctuations. As can lead to increase of clusters thermal capacity.
The conclusion has been drawn, that made in direct experiments Ni and Cu clusters because of not idealities of the external form and an internal structure cannot be applied in the devices using thermal energy of such clusters without preliminary stage of optimization. First of all, here the preliminary stage of optimization will be necessary. For example, a method of a thermal relaxation, which in some cases allows creating clusters with enough ideal spherical form and uniform internal structure. Or it is necessary to make changes to procedure of cluster synthesis for the purpose of manufacture such ideal clusters