Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
Cafetite, Ca[Ti2O5](H2O) : Crystal structure and revision of chemical formula. / Krivovichev, Sergey V.; Yakovenchuk, Victor N.; Burns, Peter C.; Pakhomovsky, Yakov A.; Menshikov, Yury P.
в: American Mineralogist, Том 88, № 2-3, 2003, стр. 424-429.Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
}
TY - JOUR
T1 - Cafetite, Ca[Ti2O5](H2O)
T2 - Crystal structure and revision of chemical formula
AU - Krivovichev, Sergey V.
AU - Yakovenchuk, Victor N.
AU - Burns, Peter C.
AU - Pakhomovsky, Yakov A.
AU - Menshikov, Yury P.
PY - 2003
Y1 - 2003
N2 - The crystal structure of cafetite, ideally Ca[Ti2O5](H2O), (monoclinic, P21ln, a = 4.9436(15), b = 12.109(4), c = 15.911(5) Å, β = 98.937(5)°, V = 940.9(5) Å3, Z = 8) has been solved by direct methods and refined to R1 = 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 Å (the average <Ti-O> bond length is 1.98 Å). 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)2Ti4O124H2O 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.
AB - The crystal structure of cafetite, ideally Ca[Ti2O5](H2O), (monoclinic, P21ln, a = 4.9436(15), b = 12.109(4), c = 15.911(5) Å, β = 98.937(5)°, V = 940.9(5) Å3, Z = 8) has been solved by direct methods and refined to R1 = 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 Å (the average <Ti-O> bond length is 1.98 Å). 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)2Ti4O124H2O 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.
UR - http://www.scopus.com/inward/record.url?scp=0037293324&partnerID=8YFLogxK
U2 - 10.2138/am-2003-2-318
DO - 10.2138/am-2003-2-318
M3 - Article
AN - SCOPUS:0037293324
VL - 88
SP - 424
EP - 429
JO - American Mineralogist
JF - American Mineralogist
SN - 0003-004X
IS - 2-3
ER -
ID: 88648950