Elastic-plastic transition in MBE-grown GaSb semiconducting crystal examined by noindentation

The present paper concerns the elastic-plastic nanodeformation of Te-doped GaSb crystals grown by molecular beam epitaxy on the n-type of GaSb substrate. The conventional analysis of nanoindentation data obtained with sharp triangular (Berkovich) and spherical tip revealed the elastic modulus (E = 83:07 1:78 GPa), hardness (H = 5:19 0:25 GPa) and “true hardness” (HT = 5:73 0:04 GPa). The registered pop-in event which indicates the elastic–plastic transition in GaSb crystal points towards the corresponding yield strength ( Y = 3:8 0:1 GPa). The origin of incipient plasticity in GaSb crystal is discussed in terms of elastic-plastic deformation energy concept

Charge-induced conformational changes of dendrimers

We study the effect of chargeable monomers on the conformation of dendrimers of low generation by computer simulations, employing bare Coulomb interactions. The presence of the latter leads to an increase in size of the dendrimer due to a combined effect of electrostatic repulsion and the presence of counterions within the dendrimer, and also enhances a shell-like structure for the monomers of different generations. In the resulting structures the bond-length between monomers, especially near the center, will increase to facilitate a more effective usage of space in the outer-regions of the dendrimer.Comment: 7 pages, 12 figure

The structure of dendrimers with charged terminal groups: Monte Carlo simulations

Taking into account the full Coulomb potential and the excluded volume interactions, properties of dendrimers with generations g = 5, 6 with charged terminal groups and counterions in an athermal solvent are examined by lattice Monte Carlo simulations. The study treats counterions explicitly and focuses on the local structure of the systems inspected by pair correlation functions g$\text{}_{ab}$ that provide information on distributions of monomers, terminal groups and ions in space at various temperatures T*. Special emphasis is placed on counterions and their role they play in causing conformational changes of the molecules. The simulations show that counterions penetrate the interior of the dendrimers, and there is a major increase in their concentration there as T* decreases. Some of them condense onto the terminal groups and a reduction in the mean effective charge ⟨Q⟩ of the dendrimers appears. Within the range of temperatures where the condensation (as a function of T*) is sharp the molecules weakly swell up when compared to their size at the other temperatures. This kind of behaviour is also reflected by the distributions of monomers and terminal groups