scholarly journals Crystal structures of 2D coordination networks in [M(bbtr)3](ClO4)2(M=Mn, Cd)

2014 ◽  
Vol 70 (a1) ◽  
pp. C1361-C1361
Author(s):  
Joachim Kusz ◽  
Maria Nowak ◽  
Robert Bronisz ◽  
Grzegorz Szklarz
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Changes ◽  
Structural Phase ◽  
Cooling Mode ◽  
Structural Modifications ◽  
Polymeric Networks ◽  
Polymeric Layer ◽  
Higher Temperature

[Fe(bbtr)3](ClO4)2 (bbtr=1,4-di(1,2,3-triazol-1-yl)butane) represents a spin crossover (SCO) system where the first coordination sphere consists of 1,2,3-triazole rings coordinated by exodentate nitrogen atoms [1]. Iron(II) ion is linked to six other iron(II) ions by bbtr ligands. This creates two dimensional (2D) polymeric layers. SCO is abrupt, accompanied by hysteresis loop. In the cooling mode P-3 -> P-1 structural phase transition precedes SCO. The non-magnetic structural transformation is accompanied by reorganization of weak intermolecular interactions and shift of 2D layers with respect to each other. Surprisingly, an analog [Fe(bbtr)3](BF4)2, does not exhibit in cooling mode neither thermally SCO nor structural phase transition [2]. To clarify the role of structural phase transition on SCO we have performed structural modifications by exchanging the kind of anions and/or metal ions. An exchange of perchlorate on triflate anion involves deeper structural changes. A topology of the polymeric layer remains the same, but the SCO is shifted to higher temperature and structural phase transition is not observed. The studies of isostructural zinc(II) analogs confirmed the crucial role of anion in the occurrence of non-magnetic structural phase transition. The [Zn(bbtr)3](ClO4)2 exhibites P-3 -> P-1 structural phase transition which is not present in tetrafluoroborate analog [2]. We expand studies on other hexacoordinating metal(II) ions. Reactions between manganese(II) or cadmium(II) perchlorates and bbtr in acetonitrile lead to [M(bbtr)3](ClO4)2 (M=Mn, Cd) complexes. Single crystal X-ray diffraction studies revealed that both compounds create a 2D polymeric networks. The temperature dependence of lattice parameters for these complexes showed that, in contrast to [Fe(bbtr)3](ClO4)2 and [Zn(bbtr)3](ClO4)2 systems, the structural phase transition is not present. This work was funded by the Polish National Science Centre Grant No. DEC-2011/01/B/ST5/06311.

The Hexagonal ↔ Orthorhombic Structural Phase Transition in Claringbullite, Cu4FCl(OH)6

2021 ◽  
Author(s):  
Mark D. Welch ◽  
Jens Najorka ◽  
Michael S. Rumsey ◽  
John Spratt
Keyword(s):  
Phase Transition ◽  
Data Storage ◽  
Structural Phase Transition ◽  
Structural Changes ◽  
Structural Phase ◽  
Magnetic Behavior ◽  
Orthorhombic Phase ◽  
New Mineral ◽  
Storage Devices ◽  
Definition Of

ABSTRACT Frustrated magnetic phases have been a perennial interest to theoreticians wishing to understand the energetics and behavior of quasi-chaotic systems at the quantum level. This behavior also has potentially wide applications to developing quantum data-storage devices. Several minerals are examples of such phases. Since the definition of herbertsmithite, Cu3ZnCl2(OH)6, as a new mineral in 2004 and the rapid realization of the significance of its structure as a frustrated antiferromagnetic phase with a triangular magnetic lattice, there has been intense study of its magnetic properties and those of synthetic compositional variants. In the past five years it has been recognized that the layered copper hydroxyhalides barlowite, Cu4BrF(OH)6, and claringbullite, Cu4FCl(OH)6, are also the parent structures of a family of kagome phases, as they also have triangular magnetic lattices. This paper concerns the structural behavior of claringbullite that is a precursor to the novel frustrated antiferromagnetic states that occur below 30 K in these minerals. The reversible hexagonal (P63/mmc) ↔ orthorhombic (Pnma or Cmcm) structural phase transition in barlowite at 200−270 K has been known for several years, but the details of the structural changes that occur through the transition have been largely unexplored, with the focus instead being on quantifying the low-temperature magnetic behavior of the orthorhombic phase. This paper reports the details of the structural phase transition in natural claringbullite at 100−293 K as studied by single-crystal X-ray diffraction. The transition temperature has been determined to lie between 270 and 293 K. The progressive disordering of Cu at the unusual trigonal prismatic Cu(OH)6 site on heating is quantified through the phase transition for the first time, and a methodology for refining this disorder is presented. Key changes in the behavior of Cu(OH)4Cl2 octahedra in claringbullite have been identified that suggest why the Pnma structure is likely stabilized over an alternative Cmcm structure. It is proposed that the presence of a non-centrosymmetric octahedron in the Pnma structure allows more effective structural relaxation during the phase transition than can be achieved by the Cmcm structure, which has only centrosymmetric octahedra.

scholarly journals Pathological transitions in myelin membranes driven by environmental and multiple sclerosis conditions

2018 ◽  
Vol 115 (44) ◽  
pp. 11156-11161 ◽  
Author(s):  
Rona Shaharabani ◽  
Maor Ram-On ◽  
Yeshayahu Talmon ◽  
Roy Beck
Keyword(s):  
Multiple Sclerosis ◽  
Phase Transition ◽  
Lipid Composition ◽  
Environmental Conditions ◽  
Structural Changes ◽  
Environmental Changes ◽  
Hexagonal Phase ◽  
Structural Phase ◽  
Structural Modifications ◽  
Transition Points

Multiple sclerosis (MS) is an autoimmune disease, leading to the destruction of the myelin sheaths, the protective layers surrounding the axons. The etiology of the disease is unknown, although there are several postulated environmental factors that may contribute to it. Recently, myelin damage was correlated to structural phase transition from a healthy stack of lamellas to a diseased inverted hexagonal phase as a result of the altered lipid stoichiometry and low myelin basic protein (MBP) content. In this work, we show that environmental conditions, such as buffer salinity and temperature, induce the same pathological phase transition as in the case of the lipid composition in the absence of MBP. These phase transitions have different transition points, which depend on the lipid’s compositions, and are ion specific. In extreme environmental conditions, we find an additional dense lamellar phase and that the native lipid composition results in similar pathology as the diseased composition. These findings demonstrate that several local environmental changes can trigger pathological structural changes. We postulate that these structural modifications result in myelin membrane vulnerability to the immune system attacks and thus can help explain MS etiology.

Primary role of the structural phase transition in the strongly coupled structure and magnetism ofLa0.835Sr0.165MnO3single crystal

1998 ◽  
Vol 57 (12) ◽  
pp. R6775-R6778 ◽  
Author(s):  
K. V. Kamenev ◽  
G. J. McIntyre ◽  
D. McK Paul ◽  
M. R. Lees ◽  
G. Balakrishnan
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Primary Role ◽  
Strongly Coupled

scholarly journals Role of thermal strain in the metal-insulator and structural phase transition of epitaxialVO2films

2016 ◽  
Vol 93 (18) ◽  
Author(s):  
V. Théry ◽  
A. Boulle ◽  
A. Crunteanu ◽  
J. C. Orlianges ◽  
A. Beaumont ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Thermal Strain ◽  
Metal Insulator

Thickness-dependent structural phase transition of strained SrRuO3ultrathin films: The role of octahedral tilt

2011 ◽  
Vol 84 (10) ◽  
Author(s):  
Seo Hyoung Chang ◽  
Young Jun Chang ◽  
S. Y. Jang ◽  
D. W. Jeong ◽  
C. U. Jung ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase

Structural phase transition in YBa2Cu3O7−δ: the role of dimensionality for high temperature superconductivity

1987 ◽  
Vol 63 (5) ◽  
pp. 385-388 ◽  
Author(s):  
Ivan K. Schuller ◽  
D.G. Hinks ◽  
M.A. Beno ◽  
D.W. Capone ◽  
L. Soderholm ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Structural Phase Transition ◽  
High Temperature Superconductivity ◽  
Structural Phase

STUDY OF ELECTRONIC STATES IN THE HYDROGEN-INDUCED STRUCTURAL PHASE TRANSITION FROM DIAMOND C(111)–(2*1) RECONSTRUCTION TO (1*1) STRUCTURE

1992 ◽  
Vol 06 (11) ◽  
pp. 649-655
Author(s):  
B. C. PAN ◽  
S. D. XIA
Keyword(s):  
Phase Transition ◽  
Electronic Structure ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Electronic States ◽  
Adsorbed Hydrogen

The electronic structure in the structural phase transition of diamond C(111) surface from (2*1) reconstruction to (1*1) structure induced by adsorbed hydrogen has been studied by DV-X αab initio calculations. The role of the adsorbed hydrogen in the structural phase transition is also discussed.

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