Structural and thermal parameters for rutile and anatase

TLDR

Neutron powder diffraction patterns of rutile and anatase TiO₂ were analyzed by the Rietveld method. The study determined precise oxygen positional parameters and anisotropic thermal parameters for rutile and anatase TiO₂, finding excellent agreement with previous neutron and X‑ray data, no significant X‑ray/neutron differences, anisotropic thermal vibrations governed by crystal stereochemistry, and Debye temperatures of 600 K for rutile and 520 K for anatase. Original source.

Abstract

Neutron powder diffraction patterns from rutile (TiO{sub 2}, P4{sub 2}/mnm, a=4.594, c=2.959A) and anatase (TiO{sub 2}, I4{sub 1}/amd, a=3.785, c=9.514A) have been analysed by the Rietveld method. The positional parameters were determined to be x{sub O}=y{sub O}=0.30478(6) in rutile and z{sub O}=0.20806(5) in anatase. The anisotropic thermal parameters were also determined. The results from this constant-wavelength neutron diffraction study are in remarkably good agreement with the results from a recently published analysis of time-of-flight neutron data from the same phases. A comparison is made with results from earlier X-ray single-crystal investigations of these polymorphs of titania, and again the agreement is good. In particular, there is no evidence for any significant difference between X-ray and neutron determinations of the oxygen position such as might have resulted from polarization effect. The thermal vibrations show marked anisotropy, which appears to be determined by the stereochemistry of the crystal structure. The Debye temperatures estimated from the diffraction data are 600(10)K for rutile and 520(10)K for anatase at room temperature. (orig.).