The Crystal Structure of Hf(OH)2SO4.

Abstract

The crystal structure of HfTe5 has been determined from three dimensional X-ray data. The structure is orthorhombic, space group Cmcm. The pycnometric density at 25.00 degC is 6.806 gcm^-3, the unit cell contains four formula units, and has the dimensions: a=3.9743(5) A, b=14.492(2) A, c=13.730(2) A. The following values were found for the positional parameters: y=0.3143(1) for Hf in 4(c); y=0.6635(2) for TeI in 4(c); y=0.9299(2), z -0.1494(2) for TeII in 8(f); y=0.2099(2), z 0.4353(2) for TeIII in 8(f). ZrTe5 is shown to be isostructural with HfTe5 (d_pycn = 6.079 gcm^-3; a =3.9876(11) A, b=14.502 A, c=13.272 A); both compounds are diagmagnetic. The HfTe5 type structure comprises distinct layers arranged approximately parallel to (010). Within the layers distorted bi-capped trigonal prisms are linked together by zig-zag chains of Te atoms. The structure and bonding in HfTe5 are discussed in relation to the ZrSe3 type structure.