Crystal Structures of Nitronium Tetranitratogallate and Its Reversible Solid-State Phase Transition Mediated by Nonmerohedral Twinning

Colombo, Daniel G.; Gladfelter, Wayne L.

doi:10.1021/ic0002418

Cited by 14 publications

(14 citation statements)

References 8 publications

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“…Indeed, this estimate is based on the assumption that the strong reflections in the orthorhombic phase are similar in intensity to the same ones in the monoclinic phase. 27,[30][31][32] Right after the orthorhombic lattice was formed ͑about 30 min after the temperature increase, which is the reference point here͒ the ratio between the orthorhombic and monoclinic I components was 0.08͑2͒, after 4.5 h it was 0.21͑2͒, after 7.8 h 0.33͑2͒, and after 9.5 h 0.30͑2͒. During the last 2.5 h at 222͑1͒ K no significant changes in the component ratio were detected.…”

Section: Formation Of the Orthorhombic Lattice And Disappearance Of Tmentioning

confidence: 99%

Tracking and understanding the first-order structural transition inEr5Si4

Mozharivskyj

Pecharsky

et al. 2004

Phys. Rev. B

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Temperature-dependent single crystal x-ray-diffraction studies revealed a reversible first-order phase transition in Er 5 Si 4 . The high-temperature phase adopts the orthorhombic Gd 5 Si 4 -type structure, and the lowtemperature phase has the monoclinic Gd 5 Si 2 Ge 2 -type structure. Unlike the magnetic/martensitic transition in Gd 5 Si 2 Ge 2 , the structural change in Er 5 Si 4 is not coupled with a magnetic transition, and the structural sequence below room temperature is just the reverse. A vibrational mode that breaks half of the interslab silicon dimers and rotates slabs in the monoclinic structure, thus lowering the symmetry from Pnma to P112 1 /a, has been identified using Landau theory. While the monoclinic phase is electronically stabilized at low temperatures, the orthorhombic phase is entropically preferable at high temperatures.

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Section: Formation Of the Orthorhombic Lattice And Disappearance Of Tmentioning

confidence: 99%

Tracking and understanding the first-order structural transition inEr5Si4

Mozharivskyj

Pecharsky

et al. 2004

Phys. Rev. B

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“…Further examples of non-merohedral twinning problems are given by Dauter (2003), Choe et al (2000), Colombo et al (2000), Gaudin et al (2000), Guelylah et al (2001), and Tang et al (2001). A worked example (Herbst-Irmer & Sheldrick, 1998) is available from http:// shelx.uni-ac.gwdg.de/~rherbst/twin.html.…”

Section: Non-merohedral Twinning: An Examplementioning

confidence: 99%

Introduction to twinning

Parsons

2003

Acta Crystallogr D Biol Crystallogr

133

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A twinned crystal is an aggregate in which different domains are joined together according to a specific symmetry operation: the twin law. The diffraction patterns derived from different domains are rotated, reflected or inverted with respect to each other, depending on the nature of the relationship between the different domains, and weighted according to the quantity of a particular domain present in the crystal. The diffraction pattern measured during data collection is a superposition of all of these. Reflections from different domains may overlap and twinned crystals fall broadly into two categories in which either all reflections or only certain zones of reflections are affected by overlap. The former occurs when a crystal lattice belongs to a higher point group than the crystal structure itself; the latter frequently occurs when the twin law is a symmetry operation belonging to a higher symmetry supercell.

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“…Consequently, metal nitrates are considered in CVD applications for the growth of C,H-free deposits. 4 The properties of complexes of semimetallic 4 (E = Sn, 3b 6 ), E(NO 3 ) 4 − (E = B, 7,8 Al, 9-13 Ga 14,15 ), E(NO 3 ) 5 2− (E = Al 10,[16][17][18][19][20] ) and E(NO 3 ) 6 q− (E = Sn, q = 2; 21 Al, 22,23 Bi, 24 q = 3). Attempts to synthesise Pb(NO 3 ) 6 2− , Ge(NO 3 ) 6 2− or Ge(NO 3 ) 4 (2b) using this method, however, failed and afforded GeO 2 and Pb(NO 3 ) 2 , respectively, instead.…”

Section: Introductionmentioning

confidence: 99%