Structural changes at the incommensurate phase transition of Na2CO3

1979 ◽  
Author(s):  
F. de Jong ◽  
F. Tuinstra
Keyword(s):  
Phase Transition ◽  
Structural Changes ◽  
Incommensurate Phase

Dynamics of the commensurate-incommensurate phase transition in C2O4D ND4, 1/2 D2O: a polarized Raman study under pressure

1993 ◽  
Vol 3 (4) ◽  
pp. 1007-1029 ◽  
Author(s):  
M. Krauzman ◽  
A. Colline ◽  
D. Kirin ◽  
R. M. Pick ◽  
N. Toupry
Keyword(s):  
Phase Transition ◽  
Incommensurate Phase ◽  
Raman Study ◽  
Polarized Raman

Incommensurate Phase Transition in a Thin Film

2011 ◽  
Vol 413 (1) ◽  
pp. 399-408 ◽  
Author(s):  
A. A. Mirkin ◽  
A. L. Pirozerskiĭ ◽  
E. V. Charnaya ◽  
Cheng Tien
Keyword(s):  
Thin Film ◽  
Phase Transition ◽  
Incommensurate Phase

Test of Critical Behaviour Through the Order Parameter-Entropy Relation in the Normal-Incommensurate Phase Transition of Rb 2 ZnCl 4

2002 ◽  
Vol 270 (1) ◽  
pp. 351-356
Author(s):  
J. M. Martín-Olalla ◽  
M. C. Gallardo ◽  
S. Ramos ◽  
J. M. Perez-Mato ◽  
E. K. H. Salje
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Incommensurate Phase ◽  
Critical Behaviour ◽  
Entropy Relation

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.

Dynamics of Discommensuration in Commensurate-Incommensurate Phase Transition of Dielectrics and Alloys

1989 ◽  
Vol 5 ◽  
pp. 115-128
Author(s):  
Kuniaki Yagi ◽  
R. Arioyshi ◽  
K. Tsuda ◽  
N. Yamamoto
Keyword(s):  
Phase Transition ◽  
Incommensurate Phase

13C NMR Study of the Incommensurate Phase Transition in [N(CH3)4]2 ZnCl4

1979 ◽  
pp. 485-490
Author(s):  
R. Blinc ◽  
M. Burgar ◽  
J. Slak ◽  
V. Rutar ◽  
F. Milia
Keyword(s):  
Phase Transition ◽  
13C Nmr ◽  
Incommensurate Phase ◽  
Nmr Study
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