Non-stoichiometric s-, p- and d-metal diborides: synthesis, properties and simulation

The results of recent studies on the synthesis, properties and simulation of the electronic structures of metal diborides are described systematically. The discovery in 2001 of superconductivity in MgB₂ with the critical transition temperature T_c≈39 K can be considered as the starting point of intensive research on diborides. The discovery of cationic sublattice non-stoichiometry for a series of s-, p- and d-metal diborides with the AlB₂-type structure was among the most interesting results. For some non-stoichiometric diborides, the homogeneity regions can be rather broad. Metal vacancies present in the diborides cause significant changes in their physicochemical properties. Methods of synthesis of cation-deficient s-, p- and d-metal diborides are discussed and the results of experimental and theoretical studies of the effect of cationic vacancies on the properties of these compounds are analysed.