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

Abstract The ternary rare earth metal boride silicide Er 3 Si 5– x B ( x = 1.17) was synthesized from the elements using the tin flux method. It crystallizes in a new structure type in the space group R 32 ( a = 6.5568(1) Å, c = 24.5541(1) Å, Z = 6). The structural arrangement can be derived from the AlB 2 structure type with boron/silicon ordering in the layered metalloid substructure made of [Si 5 B] 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 AlB 2 and Yb 3 Si 5 (Th 3 Pd 5 type). The electronic and bonding properties of Er 3 Si 5– x B were analyzed and discussed via density functional theory (DFT) calculations and a crystal orbital Hamiltonian population (COHP) bonding analysis.