Pressure effects on the Raman spectra of micelles: Pressure induced phase transition and structural changes in aqueous sodium oleatea)

1983 ◽  
Vol 78 (12) ◽  
pp. 7362-7367 ◽  
Author(s):  
P. T. T. Wong ◽  
H. H. Mantsch
Keyword(s):  
Phase Transition ◽  
Raman Spectra ◽  
Structural Changes ◽  
Pressure Effects ◽  
Aqueous Sodium

scholarly journals Pressure Effects on the Optical Properties of NdVO4

Crystals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 237 ◽  
Author(s):  
Enrico Bandiello ◽  
Josu Sánchez-Martín ◽  
Daniel Errandonea ◽  
Marco Bettinelli
Keyword(s):  
Phase Transition ◽  
Optical Properties ◽  
Absorption Band ◽  
Phase Change ◽  
Band Gap ◽  
Pressure Dependence ◽  
Structural Changes ◽  
Pressure Effects ◽  
Absorption Bands ◽  
Fundamental Absorption Band

We report on optical spectroscopic measurements in pure NdVO4 crystals at pressures up to 12 GPa. The influence of pressure on the fundamental absorption band gap and Nd3+ absorption bands has been correlated with structural changes in the crystal. The experiments indicate that a phase transition takes place between 4.7 and 5.4 GPa. We have also determined the pressure dependence of the band-gap and discussed the behavior of the Nd3+ absorption lines under compression. Important changes in the optical properties of NdVO4 occur at the phase transition, which, according to Raman measurements, corresponds to a zircon to monazite phase change. In particular, in these conditions a collapse of the band gap occurs, changing the color of the crystal. The changes are not reversible. The results are analyzed in comparison with those deriving from previous studies on NdVO4 and related vanadates.

Single Crystal Raman Spectra of the Phase Transition in KTCNQ

1982 ◽  
Vol 85 (1) ◽  
pp. 297-303 ◽  
Author(s):  
A. D. Bandrauk ◽  
K. D. Truong ◽  
S. Jandl
Keyword(s):  
Phase Transition ◽  
Single Crystal ◽  
Raman Spectra

Pressure effects on magnetic phase transition in (C2H5NH3)2CuCl4

1983 ◽  
Vol 31-34 ◽  
pp. 1191-1192 ◽  
Author(s):  
M. Chikamatsu ◽  
H. Yamazaki ◽  
K. Yamagata ◽  
H. Abe
Keyword(s):  
Phase Transition ◽  
Magnetic Phase Transition ◽  
Magnetic Phase ◽  
Pressure Effects

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.

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