Structural, Elastic and Electronic Properties of: KI and RbI Compounds

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Mualla, Zainab
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جامعة النجاح الوطنية
The structural, elastic, and electronic properties of potassium iodide (KI) and rubidium iodide (RbI) have been investigated using the full potential linearized augmented plane wave method (FP-LAPW) and the generalized gradient approximation (GGA) of the potential. The modified Becke Johnson approximation (mBJ) of the potential is used to improve the results of the electronic properties. The compounds KI and RbI are studied in the RS, CsCl, ZB, NiAs and WZ structures. The structural parameters are found to be in a very good agreement with the available theoretical and experimental results. The RS structure is found to be the ground state for both compounds. Also, the band structure results for the compounds KI and RbI have indicated a wide-band gap semiconductor behavior in all the included structures. The overall values obtained for the bulk modulus were low, denoting weak resistance to fracturing. The elastic constants are calculated for KI and RbI in RS, CsCl, ZB, NiAs and WZ structures and found to be stable according to Born's stability criteria. While the NiAs structure for RbI is found unstable. KI and RbI in all the included structures have shown ductile behavior, as well as an ionic bonding nature. Moreover, all the structures showed anisotropic nature, except RbI in WZ, which gave anisotropy factor (A) of one (Isotropic). The stiffness of the compounds was investigated using the Poisson's ratio and Cauchy's pressure. The results for KI showed that CsCl is the stiffest structure, while for RbI, RS structure was found to be the stiffest.