On the Structure of ZnI2{\rm ZnI_2}

A new structure for ${\rm ZnI_2}$ is proposed which it exists in tetragonal state. In this structure the ${\rm ZnI_2}$ molecule exists in a nonlinear array and forms the basis of the tetragonal unit cell with one basis per unit cell. The structural analysis based on the reflections listed in ASTM 30-1479 shows that the proposed structure is correct.Comment: six pages and four figures. Manuscript prepared in RevTe

Stability of the Wurtzite Structure

An analysis of available data for 20 wurtzite compounds of the ANB8-N type shows that the stability as compared with zinc blende is closely connected with deviations of the c / a ratio from the ideal value of 1.633. A simple qualitative model is proposed to account for this feature. The variation in c / a is then correlated with the charge parameter ZC / ℏωp, where Z is the (effective) valence, C Phillips's electronegativity difference, and ℏωp the plasma energy of the free-valence-electron gas. The results indicate that c / a may be predicted with an uncertainty of 0.1%

Band gap variation in laser irradiated polytypic crystals of cadmium iodide

Highly purified single crystals of cadmium iodide obtained through repeated zone refining have been subjected to laser beam exposure (Argon ion laser), both for various time durations and to various beam intensities, and then subjected to band gap determination by UV spectroscopy. The band gap has been found to decrease gradually with increase in the laser beam intensity, whereas its variation with increase in time of exposure shows an unusual behaviour such that it initially falls sharply followed by a gradual rise back to its original value. The results have been analysed and interpreted in terms of indirect band gap character of the material and an unusual variation in phonon frequency. The interpretation is well supported by X-ray diffraction and scanning electron microscopy (SEM) studies