Ag₂Ti₂P₂S₁₁: A New Layered Thiophosphate. Synthesis, Structure Determination and Temperature Dependence of the Silver Distribution

Abstract

uppermost filled levels. In the vanadium case, forThe new Ag2Ti2P2SI1 quaternary phosphosulfide instance, 'V2P2S 6' does not exist, but a mixedvalence phase viii vlI f]0.22PS3 is found instead --0.44--0.34 t disilver dititanium undecathiodiphosphate is obtained (Ouvrard, FrSour, Brec & Rouxel, 1985). The by heating the elements at ca 850K in an vanadium higher oxidation state V Ill can be isolated , 1985), which present different compound can be written as Ag2Tl z Pz ($2) S 9 . A structural patterns. To stabilize titanium oxidation Gram-Charlier anharmonic development of the atomic states other than IV, we decided to investigate the displacement factor for Ag atoms reveals a strong Ag-Ti-P-S system. non-harmonic probability density deformation, espe-The choice of silver as the M l counter-cation was cially in the direction of two empty neighbouring twofold. On the one hand, AgVP2X 6 phases had tetrahedra, away from the Ti and P cations. The already been obtained (vide supra). On the other temperature dependence of the effective one-particle hand, d l° cations are known to exhibit interesting potential shows that the Ag distribution is primarily specific characteristics, e.g. abnormally high atomic static in nature. At high temperature the tetrahedrally coordinated site is the preferential site. At lower temperature the Ag atoms are redistributed over the tetrahedral site and the adjacent triangular site. The disorder could not be resolved due to a phase transition with splitting of spots just below room temperature.

Two New Thiophosphates with Interlocked Structures: AgTi2(PS4)3 and Ag2NbTi3P6S25

“…The mean Ti}S and P}S distances indicate that the cations are in the Ti'4 and P4 states, according to their ionic radii (21). Some of the Ag atoms in both of the structures exhibit high displacement parameters in agreement with (i) the d electronic con"guration of the Ag> cations (22) and (ii) their weak localization in the tunnels of the structural frameworks.…”

Gram-Charlier development of the atomic displacement factors into mineral structures: The case of samsonite, Ag4MnSb2S6

“…Gaudin et al (1997) and van der Lee et al (1993) studied the synthetic compounds Ag 2 Ti 2 P 2 S 11 and Ag 2 MnP 2 S 6 by single-crystal X-ray diffraction and showed that the Ag atoms are observed to move from a lower coordination (triangular) to a higher coordination (tetrahedral) upon increasing the temperature. Surprisingly, in samsonite structure we observed the opposite situation with a smearing of the electron density toward the lower coordination sites with increasing the temperature.…”

“…The case of samsonite, Ag 4 MnSb 2 S 6 LUCA BINDI 1, * AND MICHEL EVAIN 2 of nonconducting materials (van der Lee et al 1993;Boucher et al 1994;Gaudin et al 1997) and of fast ion conducting phases (Kuhs and Heger 1979;Boucher et al 1992Boucher et al , 1993Evain et al 1998). Recently it has been used in solving complex structures in the pearceite-polybasite mineral family Bindi et al 2006aBindi et al , 2006bBindi et al , 2006c.…”

Preferred ion diffusion pathways and activation energies for Ag in the crystal structure of stephanite, Ag5SbS4

“…Such an approach is used to refine already known structures with suspiciously high R values and/ or high isotropic displacement parameters for Ag or Cu atoms. The non-harmonic approach has been used successfully over the past twenty years to solve numerous structures of non-conducting materials (van der Lee et al, 1993;Boucher et al, 1994;Gaudin et al, 1997) and ion-conducting phases (Kuhs and Heger, 1979;Boucher et al, 1992Boucher et al, , 1993Haile et al, 1997;Evain et al, 1998;Haile and Wuensch, 2000a,b,c). Recently, it has been used to solve complex structures of natural and synthetic sulphosalts and the pearceitepolybasite mineral family: (Evain et al, 2006a,b;Bindi et al, 2006aBindi et al, ,b, 2007; fettelite, (Bindi et al, 2009); synthetic skinnerite, (Pfitzner, 1998); synthetic tetrahedrite, (Pfitzner et al, 1997).…”