The melting and freezing with two different cooling rates of AgN (N= 140, 360, 532, 784, and 952) nanoclusters are simulated by using molecular dynamics technique with the frame work of embedded atom method. The potential energy as a function of temperature is obtained and the structural details are analyzed. The results reveal that the melting and freezing temperature increases almost linearly with the atom number of the clusters except for Ag360. All the silver nanoclusters have negative heat capacity around the phase transition temperature, and the clusters with slow cooling rate have icosahedral structure at 300 K.

Abstract

Based on preliminary research results about Compton scattering of saline solution, a linear relationship between the scattered photon counts and the concentrations had been deduced for a certain solution and it had been found that the slope of the lines was decreasing with the atomic number of the cation increasing for LiC1, NaCl and KC1(the same result for MgC1BB2BB and BaC1BB2BB) solution. Now, in order to explain such rule of the slope, the microscopic mechanism of scatterers has been studied. Through the electronic structure of hydrated ions is analyzed in detail: the distance between hydration ion and O atom after optimized, the total energy of hydration ion, the equivalent charge distribution of hydration ion and the electronic density distribution of hydration ion. At last, it is concluded that the reason of the slope decreasing when the atomic number of the alkali cation for KC1, NaCl, LiCl solutions (or MgC1BB2BB and BaClBB2BB solutions) is the bounding strength of the system on its electrons become increasing, the probability of Compton scattering is decreasing, and it will constrain the increasing velocity of the scattered photon counts.

The N-In codoped p-type ZnO films with preferential orientation along (002) plane have been fabricated on quartz glass substrates using radio frequency magnetron sputtering technique of ZnO:In2O3 powder target combining with N-implantation. The samples annealed at 700°C deserved the optimal properties, the best of which exhibits electrical characteristics with the hole concentration of 4.04×1018 cm-3, the lowest resistivity of 1.15 Ωcm and Hall mobility of about 1.35 cm2V-1s-1. The effects of post-annealing on the microstructure and electronic properties of the codoped ZnO films is analyzed via SEM, XRD, XPS and Hall measurements system, and the trend of carrier concentration with annealing time is discussed theoretically.

Fabricating small-sized Si nanoclusters has been considered as an effective approach to obtain a high figure-of-merit of thermoelectric materials. To reveal the electron and phonon transport in the Si nanoclusters with different geometric shapes, the electronic structure, the lattice dynamics and the thermoelectric properties of Si nanobox, Si nanocylinder, Si nanosphere and Si nanotetrahedron were investigated through first-principles calculation, lattice simulation and Boltzmann transport theory. The influences of the electronic structure and the lattice dynamics on the thermoelectric properties were also studied in detail. Therefore the work provides a complete understanding on the thermoelectric transport in the Si nanoclusters with different geometric shapes. Moreover, a largely enhanced figure-of-merit (ZT) at 1200 K of 1.70 has been achieved for Si nanobox.