Structural phase transitions in crystals. I. Database

Tomaszewski, Paweł E.

doi:10.1080/01411599208222899

Cited by 197 publications

(70 citation statements)

References 641 publications

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“…The Oxford control unit is calibrated at the factory using the phase change of Rochelle's salt at 109 K. 30 The factory calibration was checked in our laboratory with an iron-constantan thermocouple and an Omega 199 temperature meter. All reported temperatures are believed accurate to within 2 K. The programs SADABS 31 and TWINABS 32 were applied for absorption correction.…”

Section: X-ray Crystallographic Studiesmentioning

confidence: 99%

Reversible NO Motion in Crystalline [Fe(Porph)(1-MeIm)(NO)] Derivatives

Noll

et al. 2008

Inorg. Chem.

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The synthesis, characterization, and X-ray structures of three low-spin (nitrosyl)iron(II) tetraarylporphyrinates, [Fe(TpXPP)(NO)(1-MeIm)], where X = F (in a triclinic and a monoclinic form) and OCH 3 are reported. All three molecules, at 100 K, have a single orientation of NO. These structures are the first examples of ordered NO's in [Fe(Porph)(NO)(1-MeIm)] complexes. The three new derivatives have similar structural features including a previously unnoted "bowing" of the N NO -Fe-N Im angle caused by a concerted tilting of the axial Fe-N NO and Fe-N Im bonds. Structural features such as the displacement of Fe out of the mean porphyrin plane toward NO, tilting of the Fe-N NO bond off the heme normal, and the asymmetry of the Fe-N por bonds further strengthen and confirm observations from earlier studies. The [Fe(TpXPP)(NO)(1-MeIm)] complexes were also studied at temperatures between 125-350 K to investigate temperature-dependent variations and trends in the coordination group geometry. At varying temperatures (above 150 K), all three derivatives display a second orientation of the NO ligand. The population and depopulation of this second orientation is thermally driven, with no apparent hysteresis. Crystal packing appears to be the significant feature in defining the order/disorder of the NO ligand. The length of the bond trans to NO, Fe-N Im , was also found to be sensitive to temperature variation. The Fe-N Im bond length increases with increased temperature, whereas no other bonds change appreciably. The T-dependent Fe-N Im bond length change and cell volume changes are consistent with a "soft" Fe-N Im bond. Variable temperature measurements show that the N-O stretching frequency changes with the Fe-N Im bond length. Temperature-dependent changes in the Fe-N Im bond length and N-O stretching frequency were also found to be completely reversible with no apparent hysteresis.

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Section: X-ray Crystallographic Studiesmentioning

confidence: 99%

Reversible NO Motion in Crystalline [Fe(Porph)(1-MeIm)(NO)] Derivatives

Noll

et al. 2008

Inorg. Chem.

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“…This transition, which takes place in several binary compounds, also occurs in oxides. An interesting example is provided by Cs[LiCr]O 4 , a cotunnite-like compound at room temperature, which undergoes two phase transitions at high temperatures: one to olivine-like (Pnma) at 427 K, and a subsequent transition to anti-fluorite (F4 " 3 3m) at 573 K (Tomaszewski, 1992). The most accepted description of cotunnite depicts this structure as a set of trigonal prisms (formed by either Na atoms in Na 2 S or LiCs entities in CsLiCrO 4 ) that are occupied by the nominal anion.…”

Section: The Phases Of Na 2 S and Their Related Oxidesmentioning

confidence: 99%

“…Similar features are observed in all copper and silver chalcogenides. In the case of Ag 2 S, Tomaszewski (1992) reports the transitions: P2 1 /n ! (450 K) Im3m !…”

Section: The Phases Of Na 2 S and Their Related Oxidesmentioning

confidence: 99%

Pseudoatoms and preferred skeletons in crystals

Vegas

García-Baonza

2007

Acta Crystallogr Sect B

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The generalization of the Zintl–Klemm concept provides a universal formulation of a crystal structure in terms of universal building skeletons formed by Klemm's pseudoatoms: atoms that behave structurally according to their formal total electron charge. An important difference in this novel view is that charge is considered to be transferred, in the strict Zintl's sense, from the donor cations to the building skeleton as a whole, not specifically to a given atom or ion. Although application is restricted to (IV)–(IV) compounds (group 14 structures), the principle seems to be universal and can be applied to understand, to relate and to predict the structure of complex compounds on the basis of more simple structures, e.g. a given AB skeleton provides the building block for A 2 B, AB 2, ABX m etc. compounds of a very different nature. The application of such a principle only requires information on the constituent atoms and on the existing phases of the p-block elements (observed under ambient and high-pressure and/or high-temperature conditions). The ideas introduced here demonstrate, for the first time, that a generalization of the Zintl–Klemm concept is possible and that such a generalization helps to establish a univocal link between chemical composition (in terms of pseudoatoms) and the crystalline structures observed experimentally.

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“…1 The most widely studied compounds of the family of ␤-K 2 SO 4 are those showing phase transition, especially those with paraelectric-ferroelectric transition. 2,3 However, K 2 BeF 4 is an exception; it was studied only by Mustafaev and co-workers, 4 who observed a phase transition from Pn2 1 a to Pnam at 968 K. X-ray diffraction, thermal analysis, and Raman scattering studies on this compound have been carried out and the results are compared with those of the other compounds of the ␤-K 2 SO 4 family.…”

Section: Introductionmentioning

confidence: 99%

X-ray diffraction, thermal analysis, and Raman scattering study ofK2BeF4and comparison to other members of the
Soláns
¹
,
González-Silgo
²
,
Calvet
³

et al. 1998
Phys. Rev. B

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Thermal analysis, powder diffraction, and Raman scattering as a function of the temperature were carried out on K 2 BeF 4 . Moreover, the crystal structure was determined at 293 K from powder diffraction. The compound shows a transition from Pna2 1 to Pnam space group at 921 K with a transition enthalpy of 5 kJ/mol. The transition is assumed to be first order because the compound shows metastability. Structurally and spectroscopically the transition is similar to those observed in ͑NH 4 ͒ 2 SO 4 , which suggests that the low-temperature phase is ferroelectric. In order to confirm it, the spontaneous polarization has been computed using an ionic model. ͓S0163-1829͑98͒00309-9͔

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Structural phase transitions in crystals. I. Database

Cited by 197 publications

References 641 publications

Reversible NO Motion in Crystalline [Fe(Porph)(1-MeIm)(NO)] Derivatives

Reversible NO Motion in Crystalline [Fe(Porph)(1-MeIm)(NO)] Derivatives

Pseudoatoms and preferred skeletons in crystals

X-ray diffraction, thermal analysis, and Raman scattering study ofK2BeF4and comparison to other members of the
Soláns
¹
,
González-Silgo
²
,
Calvet
³

et al. 1998
Phys. Rev. B

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Structural phase transitions in crystals. I. Database

Cited by 197 publications

References 641 publications

Reversible NO Motion in Crystalline [Fe(Porph)(1-MeIm)(NO)] Derivatives

Reversible NO Motion in Crystalline [Fe(Porph)(1-MeIm)(NO)] Derivatives

Pseudoatoms and preferred skeletons in crystals

X-ray diffraction, thermal analysis, and Raman scattering study ofK2BeF4and comparison to other members of theSoláns1, González-Silgo2, Calvet3 et al. 1998Phys. Rev. B

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Resources

About

X-ray diffraction, thermal analysis, and Raman scattering study ofK2BeF4and comparison to other members of the
Soláns
¹
,
González-Silgo
²
,
Calvet
³

et al. 1998
Phys. Rev. B