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IntroductionThe ternary A'-B"'-C; ' chalcopyrite compounds (A' = Cu, Ag; BIT'= Al, Ga, In; and Cv'= S, Se, Te) have received considerable attention because of their academic interest and also their possible practical applications in solar cell and photodiode technologies [l]. These compounds show, at room temperature and ambient pressure, the ordered tetragonal chalcopyrite structure which may be seen as a superstructure of the zincblende phase with double primitive cell. As temperature and/or pressure rises they undergo a transition to a disordered zincblende-like structure, or to denser structures with high coordination number [2 to 161. Estimations of the isothermal bulk modulus B through semi-empirical models is of interest because of the continuity of the theory developed for other semiconductors. In this note we will use an extension of Cohen's semi-empirical model [17, 181 developed for semiconductors of groups IV, 111-V, and IILVI, and discuss the possible correlation with pressure induced phase transition values P,.

Many of AIBIIIC2VI chalcopyrite compounds show an order–disorder transition from the ordered chalcopyrite (α) to the zincblende‐like (β) phase at temperature Tc. When these compounds are alloyed with II–VI zincblende compounds according to the stoichiometric formula D2xII(AIBIII)1−xC2VI, the order–disorder transition temperature Tc decrease with the composition variable x just to a certain value xc at which all the chalcopyrite phase disappears. In this work an extension of Rincon's model, formerly used for prediction of Tc values for chalcopyrite compounds is used in order to obtain the functional behavior Tc(x) and the xc values for these alloys. The results are compared with those reported in literature.

The uniaxial stress components (USC), t, have been measured in NaCl samples, under variable pressure and temperature, in tungsten carbide (WC) toroidal anvils by energy dispersive X-ray diffraction under synchrotron radiation in a large volume Paris-Edinburgh cell. It was observed that t increases with load and at p 4.6 GPa, t À0.6 GPa (measured from the mean value of the lattice parameter of NaCl). When heating is applied (under load), t decreases, and becomes zero for T > 600 K. On cooling at constant load, t remains negligible (t 0.01 GPa) down to room temperature. After loading again (p 3.8 GPa) at room temperature, t remains small (t À0.07 GPa). A measurement of the FWHM of the diffraction peaks verifies the improvement in hydrostaticity after heating.