Electrical properties of MEM(TCNQ)2

1980 ◽  
Vol 58 (3) ◽  
pp. 334-342 ◽  
Author(s):  
M. Morrow ◽  
W. N. Hardy ◽  
J. F. Carolan ◽  
A. J. Berlinsky ◽  
Larry Weiler ◽  
...  
Keyword(s):  
Activation Energy ◽  
Heat Capacity ◽  
Dielectric Constant ◽  
Coulomb Interactions ◽  
One Dimensional ◽  
First Order ◽  
Nmr Data ◽  
First Order Transition ◽  
Electrical Data

Detailed studies of the dc and microwave conductivity and dielectric constant of the quasi-one-dimensional conductor, MEM(TCNQ)2 for 4.2 K < T < 360 K are presented. Particular attention is paid to the strong first-order transition at 335 K where the conductivity jumps by about three orders of magnitude on heating and the activation energy for the conductivity disappears. These electrical data are compared to previously published magnetic susceptibility measurements and to recent structural, heat capacity, and nmr data. The role of Coulomb interactions, in determining the temperature dependence of the conductivity, the susceptibility, and the structure, is emphasized.

Time-resolved x-ray diffraction study of one-dimensional nucleation and growth in the first-order transition

1990 ◽  
Vol 64 (6) ◽  
pp. 657-660 ◽  
Author(s):  
Naoto Metoki ◽  
Hiroyoshi Suematsu ◽  
Youichi Murakami ◽  
Yasuo Ohishi ◽  
Yasuhiko Fujii
Keyword(s):  
Diffraction Study ◽  
Nucleation And Growth ◽  
Order Transition ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
One Dimensional ◽  
X Ray ◽  
First Order ◽  
First Order Transition

scholarly journals Negative heat capacity for a Klein–Gordon oscillator in non-commutative complex phase space

2017 ◽  
Vol 14 (10) ◽  
pp. 1750141 ◽  
Author(s):  
Slimane Zaim ◽  
Hakim Guelmamene ◽  
Yazid Delenda
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Phase Space ◽  
Energy Levels ◽  
Two Dimensional ◽  
Complex Phase ◽  
First Order ◽  
Klein Gordon

We obtain exact solutions to the two-dimensional (2D) Klein–Gordon oscillator in a non-commutative (NC) complex phase space to first order in the non-commutativity parameter. We derive the exact NC energy levels and show that the energy levels split to [Formula: see text] levels. We find that the non-commutativity plays the role of a magnetic field interacting automatically with the spin of a particle induced by the non-commutativity of complex phase space. The effect of the non-commutativity parameter on the thermal properties is discussed. It is found that the dependence of the heat capacity [Formula: see text] on the NC parameter gives rise to a negative quantity. Phenomenologically, this effectively confirms the presence of the effects of self-gravitation induced by the non-commutativity of complex phase space.

scholarly journals The chiral phase transition and the role of vacuum fluctuations

2016 ◽  
Vol 31 (07) ◽  
pp. 1650025 ◽  
Author(s):  
Rashid Khan ◽  
Jens O. Andersen ◽  
Lars T. Kyllingstad ◽  
Majid Khan
Keyword(s):  
Phase Transition ◽  
Effective Potential ◽  
Chemical Potential ◽  
Chiral Limit ◽  
Vacuum Fluctuations ◽  
Physical Point ◽  
Chiral Phase ◽  
First Order ◽  
First Order Transition

We apply optimized perturbation theory to the quark–meson model at finite temperature [Formula: see text] and quark chemical potential [Formula: see text]. The effective potential is calculated to one loop both in the chiral limit and at the physical point and used to study the chiral dynamics of two-flavor QCD. The critical temperature and the order of the phase transition depend heavily on whether or not one includes the bosonic and fermionic vacuum fluctuations in the effective potential. A full one-loop calculation in the chiral limit predicts a first-order transition for all values of [Formula: see text]. At the physical point, one finds a crossover in the whole [Formula: see text]–[Formula: see text] plane.

Glass-Formers and Viscous Liquid Slowdown since David Turnbull: Enduring Puzzles and New Twists

MRS Bulletin ◽  
2008 ◽  
Vol 33 (5) ◽  
pp. 544-555 ◽  
Author(s):  
C.A. Angell
Keyword(s):  
Heat Capacity ◽  
Glass Transition ◽  
Free Volume ◽  
Homogeneous Nucleation ◽  
Liquid Metals ◽  
Order Transition ◽  
Heat Capacity Change ◽  
Pure Liquid ◽  
First Order ◽  
First Order Transition

AbstractTo Turnbull's study of the kinetic problem of nucleation and growth of crystals, we add the further enquiry into what lies behind the slow nucleation kinetics of glass-formers. Our answer to this question leads to the proposal of conditions in which a pure liquid metal, monatomic and elemental, can be vitrified. Using the case of high-pressure liquid germanium, we give electron microscope evidence for the validity of our thinking.On the question of how liquids behave when crystals do not form, Turnbull pioneered the study of glass transitions in metallic alloys, measuring the heat capacity change at the glass transition Tg for the first time, and developing with Cohen the free volume model for the temperature dependence of liquid transport properties approaching Tg. We extend the phenomenological picture to include networks where free volume does not play a role and reveal a pattern of behavior that provides for a classification of glass-formers (from “strong” to “fragile”). Where Turnbull studied supercooled liquid metals and P4 to the homogeneous nucleation limit using small droplets, we studied supercooled water in capillaries and emulsions to the homogeneous nucleation limit near −40°C. We discuss the puzzling divergences observed that are now seen as part of a cooperative transition that leads to very untypical glass-transition behavior at lower temperatures (when crystallization is bypassed by hyperquenching). Finally, we show how our interpretation of water behavior can be seen as a bridge between the behavior of the “strong” (network) liquids of classical glass science (e.g., SiO2) and the “fragile” behavior of typical molecular glass-formers. The link is made using a “Gaussian excitations” model by Matyushov and the author in which the spike in heat capacity for water is pushed by cooperativity (disorder stabilization of excitations) into a first-order transition to the ground state, at a temperature typically below Tg. In exceptional cases like triphenyl phosphite, this liquid-to-glass first-order transition lies above Tg and can be studied in detail.

A Calorimetric Study of Ammonium, Rubidium, and Potassium Hexafluophosphate

1963 ◽  
Vol 18 (2) ◽  
pp. 148-154 ◽  
Author(s):  
L. A. K. Staveley ◽  
N. R. Grey ◽  
M. J. Layzell
Keyword(s):  
Heat Capacity ◽  
Low Temperatures ◽  
Potassium Salt ◽  
Room Temperature ◽  
Entropy Change ◽  
Ammonium Ion ◽  
Calorimetric Study ◽  
First Order ◽  
Rubidium Salt ◽  
First Order Transition

Measurements have been made of the heat capacities of ammonium, rubidium, and potassium hexafluophosphate from ∼ 20°K to ∼ 300°K. The heat capacity curve of the ammonium salt shows two anomalous regions, and an order-disorder change also occurs in the rubidium salt. The potassium salt, however, undergoes a first-order transition with a large entropy change. The heat capacity of the ammonium and rubidium salts in the neighbourhood of room temperature (but not that of the potassium salt) is altered by cooling to low temperatures. In certain ranges of temperature it was unusually difficult with the rubidium salt to obtain reproducible heat capacity values. The results show that the rotation of the ammonium ion is not completely free, but they are consistent with almost free rotation in one degree of freedom and partially restricted rotation in the other two. The possible significance of the entropy changes of the various transitions is briefly discussed.

Role of Diffusion in the Shaping of the High-Absorption State in a Resonatorless Exciton Bistable System

2005 ◽  
Vol 245-246 ◽  
pp. 9-14
Author(s):  
Yuriy V. Gudyma ◽  
Ivanna V. Kruglenko
Keyword(s):  
Asymptotic Expression ◽  
Distribution Functions ◽  
Bistable System ◽  
Unified Approach ◽  
First Order ◽  
Wave Approximation ◽  
First Order Transition ◽  
Switching Wave ◽  
High Absorption

We present a unified approach to description of all the stages of shaping of a highabsorption state in a resonatorless exciton bistable system, as a nonequilibrium first-order transition. The velocity of switching wave front and thickness of interface between phases are determined within the quick switching wave approximation. The size distribution functions of subcritical and supercritical nuclei and asymptotic expression for nucleus radius were obtained.

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