Diffusion in GaN/AlN superlattices: DFT and EXAFS study

We report theoretical and experimental study of diffusion processes at GaN/AlN interfaces. Using climbing image nudged elastic band method with density functional theory (DFT) we have calculated migration barriers for vacancy-mediated self-diffusion in group-III element sublattice in AlN and GaN, for Ga diffusion in AlN and for Al diffusion in GaN. Attempt frequencies for this diffusion processes have been estimated based on harmonic transition state theory, and Al-Ga interdiffusion coefficient has been calculated. The calculations are in agreement with experimental results for GaN/AlN superlattices obtained by extended X-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy

Two molecular-type complexes of the octahedral rhenium(III) cyanocluster anion [Re6Se8(CN)6]4- with M2+ (Mn2+, Ni2+)

Two novel octahedral rhenium(III) selenocyanide cluster complexes [(nBu)(4)N](2)Ni(H2O)(5)[Re6Se8(CN)(6)].2H(2)O (1) and [(nBU)(4)N](2)Mn(H2O)(4)[Re6Se8(CN)(6)].2H(2)O (2) have been prepared by the reaction of K-4[Re6Se8(CN)(6)].3.5H(2)O, (nBu)(4)NBr kand Ni(OAC)(2) (or MnSO4) in aqueous solution. The complexes have been structurally solved in the orthorhombic unit cell Pbca with parameters: a = 19.393(2), b = 17.292(2), c = 37.255(4) Angstrom for 1, and a = 19.518(41), b = 17.488(3), c = 37.997(5) Angstrom for 2. The cluster anions and M2+ form ionic pairs (M(H2O)(n)[Re6Se8(CN)(6)])(2-) that are packed in the solid state with n-tetrabutylammonium cations. Coordinated and solvate water molecules as well as the nitrogen atoms of the anions form a network of hydrogen bonds in the structures. These compounds are isomorphous, although the coordination environments of the metal cations differ