The crystal structure of the new mineral dyrnaesite-(La), Na8CeIVREE2(PO4)6
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Standard
The crystal structure of the new mineral dyrnaesite-(La), Na8CeIVREE2(PO4)6. / Balic Zunic, Tonci.
I: Mineralogical Magazine, Bind 81, Nr. 1, 2017, s. 199-208.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - JOUR
T1 - The crystal structure of the new mineral dyrnaesite-(La), Na8CeIVREE2(PO4)6
AU - Balic Zunic, Tonci
PY - 2017
Y1 - 2017
N2 - Dyrnaesite-(La), Na7.89(Ce0.94Ca0.06)Σ1.00(La1.14Ce0.40Pr0.10Nd0.24Ca0.12)Σ2.00(PO4)6 is orthorhombic, Pnma, a = 18.4662(7), b = 16.0106(5), c = 7.0274(2) Å, V = 2077.7(1) Å3, Z = 4. The crystal structure is related to the group of Na3REE(XO4)2 compounds (with X = P, V, As), based on the aphthitalite/glaseritestructural type. Dyrnaesite is distinct in having ordered Na vacancies, and a rare-earth element (REE) site occupied preferentially by Ce4+. This also distinguishes it from closely related vitusite-(Ce) [Na3REE(PO4)2]. The relation of their unit cells is: ad = bv, bd = 3av, cd = 1/2cv. The distinct Ce4+ site in dyrnaesite-(La) has smaller coordination with shorter bond lengths than the other REE site in the same structure or the REE sites in vitusite-(Ce). It is adjacent to the predominately vacant Na site, which in its turn has the largest coordination of all Na sites in the structure. REE sites, or Na sites in a [010] row (similar to [100] in vitusite-(Ce)) assume two types of coordinations with and without mirror symmetry and two different configurations of surrounding PO4 tetrahedra. This summarizes the topological difference to vitusite-(Ce) where the corresponding coordinations are similar in the same row and intermediate in character to the two types in dyrnaesite-(La).
AB - Dyrnaesite-(La), Na7.89(Ce0.94Ca0.06)Σ1.00(La1.14Ce0.40Pr0.10Nd0.24Ca0.12)Σ2.00(PO4)6 is orthorhombic, Pnma, a = 18.4662(7), b = 16.0106(5), c = 7.0274(2) Å, V = 2077.7(1) Å3, Z = 4. The crystal structure is related to the group of Na3REE(XO4)2 compounds (with X = P, V, As), based on the aphthitalite/glaseritestructural type. Dyrnaesite is distinct in having ordered Na vacancies, and a rare-earth element (REE) site occupied preferentially by Ce4+. This also distinguishes it from closely related vitusite-(Ce) [Na3REE(PO4)2]. The relation of their unit cells is: ad = bv, bd = 3av, cd = 1/2cv. The distinct Ce4+ site in dyrnaesite-(La) has smaller coordination with shorter bond lengths than the other REE site in the same structure or the REE sites in vitusite-(Ce). It is adjacent to the predominately vacant Na site, which in its turn has the largest coordination of all Na sites in the structure. REE sites, or Na sites in a [010] row (similar to [100] in vitusite-(Ce)) assume two types of coordinations with and without mirror symmetry and two different configurations of surrounding PO4 tetrahedra. This summarizes the topological difference to vitusite-(Ce) where the corresponding coordinations are similar in the same row and intermediate in character to the two types in dyrnaesite-(La).
KW - Faculty of Science
U2 - 10.1180/minmag.2016.080.096
DO - 10.1180/minmag.2016.080.096
M3 - Journal article
VL - 81
SP - 199
EP - 208
JO - Mineralogical Magazine
JF - Mineralogical Magazine
SN - 0026-461X
IS - 1
ER -
ID: 177060326