Abstract
The crystal structure of cafetite, ideally Ca[Ti2O5](H2O), (monoclinic, P 21/ n , a = 4.9436(15), b = 12.109(4), c = 15.911(5) A, β = 98.937(5)°, V = 940.9(5) A3, Z = 8) has been solved by direct methods and refined to R 1 = 0.057 using X-ray diffraction data collected from a crystal pseudo-merohedrally twinned on (001). There are four symmetrically independent Ti cations; each is octahedrally coordinated by six O atoms. The coordination polyhedra around the Ti cations are strongly distorted with individual Ti-O bond lengths ranging from 1.743 to 2.223 A (the average bond length is 1.98 A). Two symmetrically independent Ca cations are coordinated by six and eight anions for Ca1 and Ca2, respectively. The structure is based on [Ti2O5] sheets of TiO6 octahedra parallel to (001). The Ca atoms and H2O groups are located between the sheets and link them into a three-dimensional structure. The structural formula of cafetite confirmed by electron microprobe analysis is Ca[Ti2O5](H2O), in contrast to the formula (Ca,Mg)(Fe,Al)2Ti4O12.4H2O suggested by Kukharenko et al. (1959). The wrong chemical formula suggested for cafetite by Kukharenko et al. (1959) is probably due to admixtures of magnetite or titanomagnetite in their samples. Cafetite is chemically related to kassite, CaTi2O4(OH)2, but differs from it in structure and structural formula.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.