THE LOW-FREQUENCY DIELECTRIC PROPERTIES OF ETHYLENE OXIDE AND ETHYLENE OXIDE HYDRATE

1963 ◽  
Vol 41 (6) ◽  
pp. 1424-1434 ◽  
Author(s):  
D. W. Davidson ◽  
G. J. Wilson
Keyword(s):  
Ethylene Oxide ◽  
High Frequency ◽  
Low Temperatures ◽  
Low Frequency ◽  
Dielectric Constants ◽  
Water Molecules ◽  
Kcal Mole ◽  
Absorption Region ◽  
Experimental Values ◽  
Static Dielectric Constants

The static dielectric constant of liquid ethylene oxide has been measured between 158 and 286 °K. The hydrate of ethylene oxide exhibits a dispersion–absorption region characterized by static dielectric constants about one-third as large as those of ice and by relatively large "high-frequency" dielectric constants (ε1 = 7.5 at 0 °C). This region may be approximately described as a circular arc locus, but may be represented somewhat better by a superposition of two (or three) semicircular dispersions. In either case, the activation energy for the relaxation of water molecules, to which this region is ascribed, is ca. 6.7 kcal/mole, except at low temperatures, where it becomes smaller. Experimental values of ε1 agree roughly with those calculated for comparatively rapid orientation of ethylene oxide molecules in the cavities of the hydrate. Such orientation may account for absorption maxima observed at 11 Mc/sec and above 100 Mc/sec at 90 °K.

DIELECTRIC RELAXATION IN LIQUIDS: II. ISOMERIC PENTANEDIOLS

1961 ◽  
Vol 39 (11) ◽  
pp. 2139-2154 ◽  
Author(s):  
D. W. Davidson
Keyword(s):  
Hydrogen Bonding ◽  
High Frequency ◽  
Low Temperatures ◽  
Dipole Moments ◽  
Frequency Dispersion ◽  
Liquid Structure ◽  
Dielectric Constants ◽  
Oh Groups ◽  
High Frequencies ◽  
Static Dielectric Constants

For five pentanediols the infrared spectra, the dipole moments, and the static dielectric constants show an increasing degree of internal hydrogen bonding with increasing proximity of the OH groups. The dielectric dispersion loci at low temperatures are skewed arcs over most of the dispersion range. Values of the parameter β decrease from ca. 1 to 0.55 in the series 1,5-, 1,4-, 1,2-, 2,4-, and 2,3-pentanediol, which is also the order of increasing relaxation time τ0 at low temperatures. Increased τ0 is associated with increased irregularity of intermolecular hydrogen bonding, an effect which supports the view that relaxation proceeds by a co-operative mechanism which is facilitated by regularity in the liquid structure. At temperatures of "structural relaxation", values of log τ0 are linear in (T–T∞)−1; the proportionality constants, but not the T∞'s, are the same for all five diols.The experimental behavior at relatively high frequencies departs from both the skewed-arc and Glarum equations, although less from the latter. These departures are compared with the high frequency dispersion regions in n-propanol.

Dielectric properties of the hydrates of argon and nitrogen

1968 ◽  
Vol 46 (10) ◽  
pp. 1673-1681 ◽  
Author(s):  
S. R. Gough ◽  
E. Whalley ◽  
D. W. Davidson
Keyword(s):  
Dielectric Properties ◽  
High Frequency ◽  
Dielectric Constants ◽  
Water Molecules ◽  
Circular Arc ◽  
Circular Arcs ◽  
In Series ◽  
Temperature And Pressure ◽  
Water Lattice ◽  
Static Dielectric Constants

The dielectric relaxation of water in the structure I clathrate hydrates of argon and nitrogen was studied over a range of temperature and pressure. Hydrates were slowly grown at pressures of 1 to 2 kbar in a coaxial cell enclosed in a pressure vessel. The complex permittivity loci resemble circular arcs with static dielectric constants of ~56 at 0 °C and high-frequency dielectric constants of 2.85 ± 0.05. Relaxation near 0 °C is about as slow as in ice I, but activation energies and entropies are much smaller. Formation of Bjerrum defects probably takes place preferentially near the occasional sites at which argon and nitrogen molecules have replaced water molecules in the lattice. The much faster relaxations found previously in the isostructural hydrates of ethers arise from orientational defects induced in the water lattice by the encaged molecules, a small proportion of which may form hydrogen bonds with water. The effect of small gaps in series with samples showing circular-arc dispersion behavior was evaluated.

scholarly journals Dielectric Constants of a Binary Solution Near the Critical Solution Temperature

1973 ◽  
Vol 51 (4) ◽  
pp. 545-550 ◽  
Author(s):  
I. Lubezky ◽  
R. McIntosh
Keyword(s):  
High Frequency ◽  
Binary Solution ◽  
Critical Concentration ◽  
Low Frequency ◽  
Dielectric Constants ◽  
Solution Temperature ◽  
Dielectric Losses ◽  
Theoretical Studies ◽  
Critical Solution Temperature ◽  
Experimental Knowledge

The dielectric constants and dielectric losses of solutions of nitrobenzene and 2,2,4-trimethyl pentane have been measured near the critical solution temperature over a concentration range of 22–75% by weight and in the frequency regions of 5–60 and 1000 – 4000 kHz. It was found that below a critical concentration of 35% maxima existed in ε′ and ε″ at a temperature of 0.3 °C above the critical solution temperature. At higher concentrations the maxima disappeared and phase separation was preceded only by changes in the thermal coefficients dε′/dT and dε″/dT. The present study combined with others indicates that two regions of loss exist for the system near the critical temperature: low frequency losses of a conductive nature and high frequency losses of the Debye type. The published experimental knowledge of such systems remains insufficient to enable a thorough test of the theoretical studies published recently by Snider.

DIELECTRIC EVIDENCE FOR ACETONE HYDRATE

1963 ◽  
Vol 41 (2) ◽  
pp. 264-273 ◽  
Author(s):  
G. J. Wilson ◽  
D. W. Davidson
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
High Frequency ◽  
Water System ◽  
Low Frequency ◽  
Water Molecules ◽  
Incongruent Melting ◽  
High Frequency Dielectric Constant ◽  
System A ◽  
Acetone Water

The phase diagram of the acetone–water system shows that acetone hydrate decomposes at an incongruent melting point. The existence of acetone hydrate is confirmed by a study of the low-frequency dielectric properties of this system. A dispersion region, related to the relaxation of water molecules in the clathrate structure, is characterized by a "static" dielectric constant and an activation energy about half as large as the corresponding values for ice, and by a limiting high-frequency dielectric constant of about 7 at 200° K. The magnitude of the latter is attributed to orientation of acetone molecules within the larger cavities of the hydrate structure.

scholarly journals Optical phonons polarized along the c axis of YBa2Cu3O6+x, for x = 0.5 → 0.95

1995 ◽  
Vol 73 (11-12) ◽  
pp. 663-675 ◽  
Author(s):  
C. C. Homes ◽  
T. Timusk ◽  
D. A. Bonn ◽  
R. Liang ◽  
W. N. Hardy
Keyword(s):  
High Frequency ◽  
Low Temperatures ◽  
Electronic Conductivity ◽  
Low Frequency ◽  
Phonon Spectra ◽  
Major Transformation ◽  
Low Frequency Mode ◽  
Phonon Structure ◽  
Oxygen Mode ◽  
Doping Range

The c-axis polarized phonon spectra of single crystals of YBa2Cu3O6+x, were measured for the doping range x = 0.5 → 0.95, between 10 and 300 K. The low background electronic conductivity, determined by Kramers–Kronig analysis of the reflectance, leads to a rich phonon structure. With decreased doping the five normally-active B1u modes broaden and the high-frequency apical-oxygen mode splits into two components. We associate the higher of these with the two-fold coordinated copper "sticks". The 155 cm−1 low-frequency mode, which involves the apical and the chain oxygens, splits into at least three components with decreasing doping. Some phonon anomalies that occur near Tc in the highly doped material occur well above Tc in the oxygen-reduced systems. An unusual broad phonon band develops in the normal state at ≈ 400 cm−1, which becomes more intense at low doping and low temperatures, borrowing oscillator strength from apical- and plane-oxygen modes resulting in a major transformation of the phonon spectrum below ≈150 K.

scholarly journals Optical properties and electronic polarizability of boron-antimonide semiconductor

2017 ◽  
Vol 5 (2) ◽  
pp. 43 ◽  
Author(s):  
Salah Daoud ◽  
Abdelhakim Latreche
Keyword(s):  
Optical Properties ◽  
High Frequency ◽  
Theoretical Data ◽  
Dielectric Constants ◽  
Electronic Polarizability ◽  
Micro Hardness ◽  
Plasmon Energy ◽  
Empirical Formulas ◽  
Electronegativity Difference ◽  
Static Dielectric Constants

The high-frequency and static dielectric constants, the reflex index, the total optical electronegativity difference, the bulk modulus, the micro-hardness, the plasmon energy and the electronic polarizability of cubic zincblende boron-antimonide semiconductor have been estimated by using some empirical formulas. These parameters are analyzed by comparing them against the available experimental and theoretical data. In general, our obtained results agree well with other theoretical data from the literature.

High frequency and static dielectric constants of zinc blende structured solids

2011 ◽  
Vol 151 (24) ◽  
pp. 1945-1948 ◽  
Author(s):  
A.S. Verma
Keyword(s):  
High Frequency ◽  
Dielectric Constants ◽  
Zinc Blende ◽  
Static Dielectric Constants

Some Rationale for the Unusual Behavior of the Dielectric Constant of Cu2O

1973 ◽  
Vol 51 (6) ◽  
pp. 680-685 ◽  
Author(s):  
F. L. Weichman
Keyword(s):  
Dielectric Constant ◽  
High Frequency ◽  
Low Temperatures ◽  
Low Frequency ◽  
Depletion Layer ◽  
Temperature Dependent ◽  
Unusual Behavior ◽  
Temperature Variations ◽  
Very Low Frequency ◽  
Semiconducting Material

The very low frequency dielectric constant in Cu2O varies over wide limits and is highly temperature dependent. At sufficiently low temperatures the dielectric constant for all samples reduces to the high frequency value of about 7.5. Small variations in the high frequency value are easily explained as being due to the known presence of copper crystals embedded in the semiconducting material. The low frequency and temperature variations will be related to the variation in the depletion layer formed around each copper inclusion. Calculations are based on highly oversimplified size, shape, and distribution of the copper inclusions.

Maximal results with minimal stimuli: the fewest high-frequency pulses needed to measure or model prolonged low-frequency force depression in the dorsiflexors

2021 ◽  
Author(s):  
Luca Ruggiero ◽  
Christina D. Bruce ◽  
Hannah B. Streight ◽  
Chris J. McNeil
Keyword(s):  
Gold Standard ◽  
High Frequency ◽  
Low Frequency ◽  
Pulse Number ◽  
Limits Of Agreement ◽  
Force Depression ◽  
Before And After ◽  
Minimum Number ◽  
Experimental Values ◽  
Further Development

Quantifying prolonged low-frequency force depression (PLFFD) with the gold-standard 1-s trains presents challenges so paired-pulses have been used. Owing to greater impairment of high-frequency doublet than tetanic torque, paired-pulses underestimate PLFFD. This study aimed to approximate the minimum number of high-frequency pulses needed to avoid such underestimation and assess the feasibility of modelling PLFFD from a limited number of experimental pulses. In 13 participants, a 1-s 10-Hz train and 100-Hz trains with 2, 4, 7, 12, 15, 25, 50, or 100 pulses were evoked before and after (15 min, 2, 4, and 7 d) eccentric exercise of the dorsiflexors. With ≤ 12 pulses, impairment of 100-Hz torque was greater than the 1-s train (P ≤ 0.05; e.g., 12 vs. 100 pulses at 4d: 97.8 ± 8.5% vs. 100.5 ± 8.2% baseline). Consequently, with ≤ 12 pulses, PLFFD was underestimated compared to the gold-standard measure (P ≤ 0.05; e.g., 12 vs. 100 pulse 10:100 Hz torque ratio at 4d: 86.8 ± 12.8% vs. 84.6 ± 13.5% baseline). Modelling reproduced 10:100 Hz ratios (PLFFD) with 95% limits of agreement of −13.6-16.7% of experimental values with ≥ 12 pulses. Our results indicate that a minimum of 13-25 100-Hz pulses are needed to accurately quantify PLFFD in the dorsiflexors. Although this may not be the minimum range for other muscles, a similar relationship with pulse number likely exists. Modelling may eventually provide an option to estimate PLFFD from experimental trains with relatively few pulses; however, further development is imperative to reduce variability.

Dielectric Properties of Semiconductors by TDDFT in Real-Space and Real-Time Approach

2004 ◽  
Vol 829 ◽  
Author(s):  
Yasunari Zempo ◽  
Nobuhiko Akino
Keyword(s):  
Real Time ◽  
Density Functional ◽  
Real Space ◽  
Dielectric Constants ◽  
Functional Theory ◽  
The Real ◽  
Function Change ◽  
Experimental Values ◽  
Static Dielectric Constants ◽  
Band Separation

ABSTRACTThe dielectric responses of semiconductors such as C, Ge, Si, and AlGaAs are studied by the time-dependent density-functional theory. In our study, the real-space grid representation of the electron wave functions is used and the real-time approach is employed for the dynamics of the system. Both the static and dynamic dielectric functions are calculated, and we yielded that the static dielectric constants ε(0) are especially in good agreement with the experimental values. The effect of Al-component in the compound semiconductor AlxGa1−xAs is also studied. The peaks of the imaginary part of the dielectric function change with the band separation as a function of the Al-component. Furthermore, the static dielectric constants show the expected change due to the band separation as a function of the Al-component.

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