Phase Transitions, Superconductivity, and Ferromagnetism in Fullerene Systems

MRS Bulletin ◽  
1994 ◽  
Vol 19 (11) ◽  
pp. 28-30 ◽  
Author(s):  
C.N.R. Rao ◽  
Ram Seshadri
Keyword(s):  
Solid State ◽  
Alkaline Earth ◽  
Point Group ◽  
Group Symmetry ◽  
High Electron ◽  
Chemical Transformations ◽  
Disordered Solids ◽  
High Electron Affinity ◽  
Centers Of Mass ◽  
Image Position

By virtue of their unique structures, fullerenes exhibit novel chemical transformations. Particularly pertinent to this article are the interesting properties exhibited by fullerenes in the solid state. These molecules are spherical or near-spherical in shape. Molecules with high point-group symmetry, which are not bound strongly in the solid state, tend to crystallize into structures with long-range periodicity of the molecular centers of mass, but the molecular orientations are random or even dynamically disordered. When dynamically disordered, themolecules rotate about some preferred axis. C60 and C70 satisfy the criteria for such orientationally disordered solids and exhibit rich phase behavior in the solid state. Since C60 has high electron affinity, it forms anion salts with alkali and alkaline-earth metals as well as with strong organic donor molecules. With tetrakis dimethylaminoethylene (TDAE), which is a very powerful electron donor, C60 forms a 1:1 solid that is ferromagnetic. C60-TDAE is the molecular organic ferromagnet with the highest Tc (of 16 K) known to date. Some of the alkali and alkaline-earth fullerides, on the other hand, show superconductivity, with transition temperatures going up to 33K. We shall briefly examine some of these solid-state properties.

Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium Lutetium Fluoride (KLF) Microcrystals

2020 ◽  
Author(s):  
Xiaojing Xia ◽  
Anupum Pant ◽  
Xuezhe Zhou ◽  
Elena Dobretsova ◽  
Alex Bard ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Solid State ◽  
Information Science ◽  
Point Group ◽  
Solid State Laser ◽  
Lanthanide Ions ◽  
Group Symmetry ◽  
Luminescence Spectra ◽  
Crystalline Phases ◽  
State Laser

Fluoride crystals, due to their low phonon energies, are attractive hosts of trivalent lanthanide ions for applications in upconverting phosphors, quantum information science, and solid-state laser refrigeration. In this article, we report the rapid, low-cost hydrothermal synthesis of potassium lutetium fluoride (KLF) microcrystals for applications in solid-state laser refrigeration. Four crystalline phases were synthesized, namely orthorhombic K<sub>2</sub>LuF<sub>5</sub> (Pnma), trigonal KLuF<sub>4</sub> (P3<sub>1</sub>21), orthorhombic KLu<sub>2</sub>F<sub>7</sub> (Pna2<sub>1</sub>), and cubic KLu<sub>3</sub>F<sub>10</sub> (Fm3m), with each phase exhibiting unique microcrystalline morphologies. Luminescence spectra and emission lifetimes of the four crystalline phases were characterized based on the point-group symmetry of trivalent cations. Laser refrigeration was measured by observing both the optomechanical eigenfrequencies of microcrystals on cantilevers in vacuum, and also the Brownian dynamics of optically trapped microcrystals in water. Among all four crystalline phases, the most significant cooling was observed for 10%Yb:KLuF<sub>4</sub> with cooling of 8.6 $\pm$ 2.1 K below room temperature. Reduced heating was observed with 10%Yb:K<sub>2</sub>LuF<sub>5</sub>

scholarly journals Spin-reversal energy barriers of 305 K for Fe2+ d6 ions with linear ligand coordination

Nanoscale ◽  
2017 ◽  
Vol 9 (30) ◽  
pp. 10596-10600 ◽  
Author(s):  
Lei Xu ◽  
Ziba Zangeneh ◽  
Ravi Yadav ◽  
Stanislav Avdoshenko ◽  
Jeroen van den Brink ◽  
...  
Keyword(s):  
Solid State ◽  
Magnetic Anisotropy ◽  
Point Group ◽  
Group Symmetry ◽  
Point Group Symmetry ◽  
State Matrix ◽  
Magnetic Anisotropy Energy ◽  
Spin Reversal ◽  
Ligand Coordination ◽  
Li Ion

A remarkably large magnetic anisotropy energy of 305 K is computed by quantum chemistry methods for divalent Fe2+ d6 substitutes at Li-ion sites with D6h point-group symmetry within the solid-state matrix of Li3N.

scholarly journals Crystal structures of two alkaline earth (M= Ba and Sr) dimanganese(II) iron(III) tris(orthophosphates)

2017 ◽  
Vol 73 (5) ◽  
pp. 767-770
Author(s):  
Ghaleb Alhakmi ◽  
Abderrazzak Assani ◽  
Mohamed Saadi ◽  
Lahcen El Ammari
Keyword(s):  
Crystal Structures ◽  
Alkaline Earth ◽  
Point Group ◽  
Three Dimensional ◽  
Group Symmetry ◽  
Solid State Reactions ◽  
Site Symmetry ◽  
Orthorhombic System ◽  
Group Type ◽  
Alkaline Earth Cations

Two new orthophosphates, BaMn2Fe(PO4)3[barium dimanganese(II) iron(III) tris(orthophosphate)] and SrMn2Fe(PO4)3[strontium dimanganese(II) iron(III) tris(orthophosphate)], were synthesized by solid-state reactions. They are isotypic and crystallize in the orthorhombic system with space group typePbcn. Their crystal structures comprise infinite zigzag chains of edge-sharing FeO6octahedra (point group symmetry .2.) and Mn2O10double octahedra running parallel to [001], linked by two types of PO4tetrahedra. The so-formed three-dimensional framework delineates channels running along [001], in which the alkaline earth cations (site symmetry .2.) are located within a neighbourhood of eight O atoms.

Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium Lutetium Fluoride (KLF) Microcrystals

2020 ◽  
Author(s):  
Xiaojing Xia ◽  
Anupum Pant ◽  
Xuezhe Zhou ◽  
Elena Dobretsova ◽  
Alex Bard ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Solid State ◽  
Information Science ◽  
Point Group ◽  
Solid State Laser ◽  
Lanthanide Ions ◽  
Group Symmetry ◽  
Luminescence Spectra ◽  
Crystalline Phases ◽  
State Laser

Fluoride crystals, due to their low phonon energies, are attractive hosts of trivalent lanthanide ions for applications in upconverting phosphors, quantum information science, and solid-state laser refrigeration. In this article, we report the rapid, low-cost hydrothermal synthesis of potassium lutetium fluoride (KLF) microcrystals for applications in solid-state laser refrigeration. Four crystalline phases were synthesized, namely orthorhombic K<sub>2</sub>LuF<sub>5</sub> (Pnma), trigonal KLuF<sub>4</sub> (P3<sub>1</sub>21), orthorhombic KLu<sub>2</sub>F<sub>7</sub> (Pna2<sub>1</sub>), and cubic KLu<sub>3</sub>F<sub>10</sub> (Fm3m), with each phase exhibiting unique microcrystalline morphologies. Luminescence spectra and emission lifetimes of the four crystalline phases were characterized based on the point-group symmetry of trivalent cations. Laser refrigeration was measured by observing both the optomechanical eigenfrequencies of microcrystals on cantilevers in vacuum, and also the Brownian dynamics of optically trapped microcrystals in water. Among all four crystalline phases, the most significant cooling was observed for 10%Yb:KLuF<sub>4</sub> with cooling of 8.6 $\pm$ 2.1 K below room temperature. Reduced heating was observed with 10%Yb:K<sub>2</sub>LuF<sub>5</sub>

Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium Lutetium Fluoride (KLF) Microcrystals

2020 ◽  
Author(s):  
Xiaojing Xia ◽  
Anupum Pant ◽  
Xuezhe Zhou ◽  
Elena Dobretsova ◽  
Alex Bard ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Solid State ◽  
Information Science ◽  
Point Group ◽  
Solid State Laser ◽  
Lanthanide Ions ◽  
Group Symmetry ◽  
Luminescence Spectra ◽  
Crystalline Phases ◽  
State Laser

Fluoride crystals, due to their low phonon energies, are attractive hosts of trivalent lanthanide ions for applications in upconverting phosphors, quantum information science, and solid-state laser refrigeration. In this article, we report the rapid, low-cost hydrothermal synthesis of potassium lutetium fluoride (KLF) microcrystals for applications in solid-state laser refrigeration. Four crystalline phases were synthesized, namely orthorhombic K<sub>2</sub>LuF<sub>5</sub> (Pnma), trigonal KLuF<sub>4</sub> (P3<sub>1</sub>21), orthorhombic KLu<sub>2</sub>F<sub>7</sub> (Pna2<sub>1</sub>), and cubic KLu<sub>3</sub>F<sub>10</sub> (Fm3m), with each phase exhibiting unique microcrystalline morphologies. Luminescence spectra and emission lifetimes of the four crystalline phases were characterized based on the point-group symmetry of trivalent cations. Laser refrigeration was measured by observing both the optomechanical eigenfrequencies of microcrystals on cantilevers in vacuum, and also the Brownian dynamics of optically trapped microcrystals in water. Among all four crystalline phases, the most significant cooling was observed for 10%Yb:KLuF<sub>4</sub> with cooling of 8.6 $\pm$ 2.1 K below room temperature. Reduced heating was observed with 10%Yb:K<sub>2</sub>LuF<sub>5</sub>

Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium Lutetium Fluoride (KLF) Microcrystals

2020 ◽  
Author(s):  
Xiaojing Xia ◽  
Anupum Pant ◽  
Xuezhe Zhou ◽  
Elena Dobretsova ◽  
Alex Bard ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Solid State ◽  
Information Science ◽  
Point Group ◽  
Solid State Laser ◽  
Lanthanide Ions ◽  
Group Symmetry ◽  
Luminescence Spectra ◽  
Crystalline Phases ◽  
State Laser

Fluoride crystals, due to their low phonon energies, are attractive hosts of trivalent lanthanide ions for applications in upconverting phosphors, quantum information science, and solid-state laser refrigeration. In this article, we report the rapid, low-cost hydrothermal synthesis of potassium lutetium fluoride (KLF) microcrystals for applications in solid-state laser refrigeration. Four crystalline phases were synthesized, namely orthorhombic K<sub>2</sub>LuF<sub>5</sub> (Pnma), trigonal KLuF<sub>4</sub> (P3<sub>1</sub>21), orthorhombic KLu<sub>2</sub>F<sub>7</sub> (Pna2<sub>1</sub>), and cubic KLu<sub>3</sub>F<sub>10</sub> (Fm3m), with each phase exhibiting unique microcrystalline morphologies. Luminescence spectra and emission lifetimes of the four crystalline phases were characterized based on the point-group symmetry of trivalent cations. Laser refrigeration was measured by observing both the optomechanical eigenfrequencies of microcrystals on cantilevers in vacuum, and also the Brownian dynamics of optically trapped microcrystals in water. Among all four crystalline phases, the most significant cooling was observed for 10%Yb:KLuF<sub>4</sub> with cooling of 8.6 $\pm$ 2.1 K below room temperature. Reduced heating was observed with 10%Yb:K<sub>2</sub>LuF<sub>5</sub>

scholarly journals Structure cristalline de type alluaudite KNa5Mn3(MoO4)6

2015 ◽  
Vol 71 (1) ◽  
pp. 69-72 ◽  
Author(s):  
Chahira Bouzidi ◽  
Wafa Frigui ◽  
Mohamed Faouzi Zid
Keyword(s):  
Solid State ◽  
Point Group ◽  
Three Dimensional ◽  
Group Symmetry ◽  
Dimensional Structure ◽  
Site Symmetry ◽  
Structural Description ◽  
Point Group Symmetry ◽  
The Third ◽  
New Phase

The new phase potassium pentasodium trimanganese hexakis(molybdate), KNa5Mn3Mo6O24, has been synthesized using solid-state methods. The structure is composed ofM2O10(M= Mn, Na) dimers and MoO4tetrahedra (point group symmetry 2) sharing corners and forming layers parallel to (100), which are linkedviacommon corners of another type ofMO4tetrahedra, forming a three-dimensional structure with two types of large channels along [001] in which two types of Na+cations (one with site symmetry 2, one with -1) and K+cations (site symmetry 2, half-occupation) are located. Mn2+and the third type of Na+cations are located at the same siteMwith occupancies of 0.75 and 0.25, respectively. A comparative structural description is provided between the structure of the title compound and those of the related phases Cu1.35Fe3(PO4)3and NaAgFeMn2(PO4)3.

scholarly journals Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium Lutetium Fluoride (KLF) Microcrystals

2020 ◽  
Author(s):  
Xiaojing Xia ◽  
Anupum Pant ◽  
Xuezhe Zhou ◽  
Elena Dobretsova ◽  
Alex Bard ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Solid State ◽  
Information Science ◽  
Point Group ◽  
Solid State Laser ◽  
Lanthanide Ions ◽  
Group Symmetry ◽  
Luminescence Spectra ◽  
Crystalline Phases ◽  
State Laser

Fluoride crystals, due to their low phonon energies, are attractive hosts of trivalent lanthanide ions for applications in upconverting phosphors, quantum information science, and solid-state laser refrigeration. In this article, we report the rapid, low-cost hydrothermal synthesis of potassium lutetium fluoride (KLF) microcrystals for applications in solid-state laser refrigeration. Four crystalline phases were synthesized, namely orthorhombic K<sub>2</sub>LuF<sub>5</sub> (Pnma), trigonal KLuF<sub>4</sub> (P3<sub>1</sub>21), orthorhombic KLu<sub>2</sub>F<sub>7</sub> (Pna2<sub>1</sub>), and cubic KLu<sub>3</sub>F<sub>10</sub> (Fm3m), with each phase exhibiting unique microcrystalline morphologies. Luminescence spectra and emission lifetimes of the four crystalline phases were characterized based on the point-group symmetry of trivalent cations. Laser refrigeration was measured by observing both the optomechanical eigenfrequencies of microcrystals on cantilevers in vacuum, and also the Brownian dynamics of optically trapped microcrystals in water. Among all four crystalline phases, the most significant cooling was observed for 10%Yb:KLuF<sub>4</sub> with cooling of 8.6 $\pm$ 2.1 K below room temperature. Reduced heating was observed with 10%Yb:K<sub>2</sub>LuF<sub>5</sub>

Symmetry relationship in electron beam induced phase transitions

1989 ◽  
Vol 47 ◽  
pp. 500-501
Author(s):  
J. P. Zhang ◽  
L. D. Marks
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Oxygen Content ◽  
Transition Metal Oxides ◽  
Selection Rule ◽  
Point Group ◽  
Group Symmetry ◽  
Lower Oxygen ◽  
Image Position ◽  
New Phase

In this work we present a symmetry rule for the phase transitions in transition metal oxides driven by DIET of oxygen in an electron microscope. The phase transitions are to a structure with a higher point group symmetry. The new phase with a lower oxygen content is either one with a supergroup symmetry with respect to the original phase, or an amorphous intermediary. If a possible lower oxygen content phase does not have the correct supergroup symmetry, it is not formed. Of this type are the phase transitions in TiO2, MoO3, WO3, V2O5 and Ta2o5 of which the experimental results are listed in the first section of Table 1. It is also found that the point group is conserved during the phase transition if the oxide belongs to the highest groups Oh or D6h, for instance NiO, CoO and ZnO. This symmetry selection rule can therefore be used to predict the route of the phase transition. The selection rule is:

Vibrational spectra of arsenic triiodide

1968 ◽  
Vol 21 (10) ◽  
pp. 2379 ◽  
Author(s):  
MA Hooper ◽  
DW James
Keyword(s):  
Raman Spectrum ◽  
Solid State ◽  
Vibrational Spectra ◽  
Point Group ◽  
Group Symmetry ◽  
Space Group Symmetry ◽  
Space Group ◽  
Polarization Studies

The Raman spectrum of AsI3 has been determined in solution in CS2 and in the solid state. For the solution the assignment of Stammreich, Forneris, and Tavares has been confirmed by polarization studies. In the solid state it is shown that assignment of the spectrum is only possible on the basis of space group symmetry and an earlier assignment based on point group C3v is in error. The solid state frequencies (R3 symmetry) are v1(Ag) 185 cm-l, v2(Ag) 75 cm-l, v3(Au) 201 cm-l, v4(Au) 102 cm-1, v5(Eg) 205 cm-1, v6(Eg) 50 cm-l, v7(Eg) 216 cm-1, v8(Eg) 74 cm-1.

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