Electron deformation density in titanium diboride chemical bonding in TiB2

Abstract Titanium diboride, TiB 2 , crystallizes in the AlB 2 -type structure, hexagonal P 6/ mmm . The conventional, free atom crystal structure refinement led to R =2.23%, and including extinction corrections to R =1.58%. Multipole refinements with multipoles up to order four (hexadecapole) reduced the R value to 1.21%. Difference density maps revealed charge deficiencies on the boron sites and broadbands of charge accumulations between the boron atoms indicating a graphitic B-delocalization of the boron sp 2 hybrid orbitals.