Flux synthesis, crystal structure and electronic properties of the layered rare earth metal boride silicide Er3Si5-xB. An example of a boron/silicon-ordered structure derived from the AlB2 structure type

The ternary rare earth metal boride silicide Er3Si5-xB (x = 1.17) was synthesized from the elements using the tin flux method. It crystallizes in a new structure type in the space group R32 (a = 6.5568(1) angstrom, c = 24.5541(1) angstrom, Z = 6). The structural arrangement can be derived from the AlB2 structure type with boron/silicon ordering in the layered metalloid substructure made of [Si5B] hexagons. The presence or absence of the boron atoms involved in this ordered structure is discussed on the basis of difference Fourier syntheses and structural analysis, in relation with the binary parent structures AlB2 and Yb3Si5 (Th3Pd5 type). The electronic and bonding properties of Er3Si5-xB were analyzed and discussed via density functional theory (DFT) calculations and a crystal orbital Hamiltonian population (COHP) bonding analysis.