Calculation of the ν4 (NH4+) IR Mode Frequency and the Damping Constant (FWHM) close to the Phase Transitions in NH4ZN(HCOO)3 and ND4ZN(DCOO)3

Measurements of the temperature dependence of the nuclear quadrupole resonance (NQR) frequencies and spin–lattice relaxation times for the 35Cl nuclei in Cs2PtCl6, Rb2PtCl6, K2PtCl6, and K2PdCl6 provide information on the temperature dependence of two averages of the rotary lattice mode frequency over the-Brillouin zone. An iterative method is introduced to analyze the NQR frequency data and simultaneously yield the static lattice resonance frequencies and the temperature dependence of one of the average rotary mode frequencies. The results show that previous analyses of the data yielded erroneous values of the static lattice resonance frequencies. What is more interesting, the analysis presented clearly indicates incipient phase transitions in both K2PtCl6 and K2PdCl6 but shows that the structures of Cs2PtCl6 and Rb2PtCl6 remain stable to 0 K. The interpretation of the relaxation time data yields the temperature dependence of the second average rotary mode frequency and substantiates the conclusions drawn from the frequency data. A comparison of data for K2PtCl6 and K2IrCl6 reveals an incipient phase transition in the latter substance as well.

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Phase transitions, symmetry breaking and asymptotic properties of the goldstone-mode frequency

Physica ◽

10.1016/0031-8914(73)90165-1 ◽

1973 ◽

Vol 67 (3) ◽

pp. 521-532 ◽

Cited By ~ 11

Author(s):

T. Schneider ◽

P.F. Meier

Keyword(s):

Phase Transitions ◽

Symmetry Breaking ◽

Asymptotic Properties ◽

Mode Frequency ◽

Goldstone Mode

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Electron Microscopy of Graphite Intercalation Compounds

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055564 ◽

1982 ◽

Vol 40 ◽

pp. 544-545

Author(s):

G. Timp ◽

L. Salamanca-Riba ◽

L.W. Hobbs ◽

G. Dresselhaus ◽

M.S. Dresselhaus

Keyword(s):

Electron Microscopy ◽

Phase Transitions ◽

Domain Wall ◽

Intercalation Compounds ◽

Lattice Plane ◽

Wall Model ◽

Graphite Intercalation Compounds ◽

Fundamental Symmetry ◽

Graphite Intercalation

Electron microscopy can be used to study structures and phase transitions occurring in graphite intercalations compounds. The fundamental symmetry in graphite intercalation compounds is the staging periodicity whereby each intercalate layer is separated by n graphite layers, n denoting the stage index. The currently accepted model for intercalation proposed by Herold and Daumas assumes that the sample contains equal amounts of intercalant between any two graphite layers and staged regions are confined to domains. Specifically, in a stage 2 compound, the Herold-Daumas domain wall model predicts a pleated lattice plane structure.

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Multiple phase transitions investigated by high-speed TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100175880 ◽

1990 ◽

Vol 48 (4) ◽

pp. 550-551

Author(s):

Oleg Bostanjoglo ◽

Peter Thomsen-Schmidt

Keyword(s):

Phase Transitions ◽

High Speed ◽

Short Exposure ◽

Semiconductor Film ◽

Time Resolved ◽

Short Exposure Time ◽

Multiple Phase ◽

Model Substance ◽

History Of ◽

Electron Image

Thin GexTe1-x (x = 0.15-0.8) were studied as a model substance of a composite semiconductor film, in addition being of interest for optical storage material. Two complementary modes of time-resolved TEM were used to trace the phase transitions, induced by an attached Q-switched (50 ns FWHM) and frequency doubled (532 nm) Nd:YAG laser. The laser radiation was focused onto the specimen within the TEM to a 20 μm spot (FWHM). Discrete intermediate states were visualized by short-exposure time doubleframe imaging /1,2/. The full history of a transformation was gained by tracking the electron image intensity with photomultiplier and storage oscilloscopes (space/time resolution 100 nm/3 ns) /3/. In order to avoid radiation damage by the probing electron beam to detector and specimen, the beam is pulsed in this continuous mode of time-resolved TEM,too.Short events ( <2 μs) are followed by illuminating with an extended single electron pulse (fig. 1c)

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