Classification of borides

Abstract Until now, the bondes, which represent one of the most important classes of refractory compounds, have not been classified completely. The effect of various factors such as the size, the crystal chemistry, the valency, the electron concentration, the electron structures of the metal and of the boron atoms and the effect that structural peculiarities of the borides have on the formation of a definite type of chemical bonding in the borides have been analysed. It has been shown that all these factors are associated with one another and depend on the position of the elements in the periodic table. As a result, for the first time we propose a classification of the borides based on the ability of the interacting atoms of boron and other elements to form stable configurations with various stabilities of the localized part of valence electrons. According to the classification proposed, all the metal borides are divided into three classes, each class containing two groups which differ in their type of chemical bond.