Quantum effects near the liquid–vapour critical point

1990 ◽  
Vol 68 (4-5) ◽  
pp. 449-453
Author(s):  
John R. de Bruyn ◽  
David A. Balzarini
Keyword(s):  
Critical Point ◽  
Critical Exponents ◽  
Qualitative Agreement ◽  
Room Temperature ◽  
Quantum Effects ◽  
Coexistence Curve ◽  
Quantum Fluids ◽  
Amplitude Ratios ◽  
Theoretical Predictions ◽  
Critical Amplitudes

We gather together a number of recent measurements of the coexistence curve and compressibility of fluids close to the critical point, and investigate the variation of the critical exponents and amplitudes as quantum effects become more important. We find that the universal critical exponents and amplitude ratios are the same for quantum fluids as for room-temperature fluids, as expected. Some of the nonuniversal critical amplitudes, however, show systematic variations as quantum effects become significant, in at least qualitative agreement with theoretical predictions.

A crystallographic analysis of the CoSi/Si(111) interface using Transmission Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 574-575
Author(s):  
A.C. Daykin ◽  
C.J. Kiely ◽  
R.C. Pond ◽  
J.L. Batstone
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Structure ◽  
Room Temperature ◽  
Theoretical Method ◽  
Crystallographic Analysis ◽  
Si Substrate ◽  
Transmission Electron ◽  
Theoretical Predictions

When CoSi2 is grown onto a Si(111) surface it can form in two distinct orientations. A-type CoSi2 has the same orientation as the Si substrate and B-type is rotated by 180° degrees about the [111] surface normal.One method of producing epitaxial CoSi2 is to deposit Co at room temperature and anneal to 650°C.If greater than 10Å of Co is deposited then both A and B-type CoSi2 form via a number of intermediate silicides .The literature suggests that the co-existence of A and B-type CoSi2 is in some way linked to these intermediate silicides analogous to the NiSi2/Si(111) system. The phase which forms prior to complete CoSi2 formation is CoSi. This paper is a crystallographic analysis of the CoSi2/Si(l11) bicrystal using a theoretical method developed by Pond. Transmission electron microscopy (TEM) has been used to verify the theoretical predictions and to characterise the defect structure at the interface.

Room-Temperature Chemical Synthesis of C2

2019 ◽  
Author(s):  
Kazunori Miyamoto ◽  
Shodai Narita ◽  
Yui Masumoto ◽  
Takahiro Hashishin ◽  
Mutsumi Kimura ◽  
...  
Keyword(s):  
Chemical Synthesis ◽  
Ground State ◽  
Room Temperature ◽  
Chemical Species ◽  
Quadruple Bond ◽  
Photon Excitation ◽  
Physical Energy ◽  
Theoretical Predictions ◽  
Carbon Arc ◽  
Inherent Nature

Diatomic carbon (C<sub>2</sub>) is historically an elusive chemical species. It has long been believed that the generation of C<sub>2 </sub>requires extremely high “physical” energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C<sub>2 </sub><i>in the ground state </i>is experimentally inaccessible. Here, we present the first “chemical” synthesis of C<sub>2 </sub>in a flask at <i>room temperature or below</i>, providing the first experimental evidence to support theoretical predictions that (1) C<sub>2 </sub>has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that (2) C<sub>2 </sub>serves as a molecular element in the formation of sp<sup>2</sup>-carbon allotropes such as graphite, carbon nanotubes and C<sub>60</sub>.

The electrical resistivity of lithium-6

1961 ◽  
Vol 263 (1314) ◽  
pp. 407-419 ◽  
Keyword(s):  
Electrical Resistivity ◽  
Isotopic Composition ◽  
Specific Heat ◽  
Room Temperature ◽  
Natural Isotopic Composition ◽  
Square Roots ◽  
Conduction Electrons ◽  
Ionic Mass ◽  
Theoretical Predictions ◽  
Electrical Resistivities

The electrical resistivities of lithium -6 and lithium of natural isotopic composition have been studied between 4°K and room temperature. In addition, their absolute resistivities have been carefully compared at room temperature. These measurements show that the effect of ionic mass on electrical resistivity agrees with simple theoretical predictions, namely, that the properties of the conduction electrons in lithium do not depend on the mass of the ions, and that the characteristic lattice frequencies for the two pure isotopes are in the inverse ratio of the square roots of their ionic masses. A comparison with the specific heat results of Martin (1959, 1960), where the simple theory is found not to hold, indicates the possibility that anharmonic effects are present which affect the specific heat but not the electrical resistivity.

Experimental Verification of Constitutive Equations for Creep and Plasticity Based on Overlay Models

1983 ◽  
Vol 105 (3) ◽  
pp. 277-284 ◽  
Author(s):  
P. Meijers ◽  
F. Roode
Keyword(s):  
Plastic Deformation ◽  
Room Temperature ◽  
304 Stainless Steel ◽  
Model Parameters ◽  
General Description ◽  
Time Effects ◽  
Plastic Deformations ◽  
Biaxial Load ◽  
Theoretical Predictions ◽  
Good Agreement

A general description of creep and plastic deformation based on overlay models is presented. This includes the description of time effects during plastic deformation at room temperature. A detailed procedure to obtain the model parameters is also discussed. The description has been evaluated for a large number of uniaxial and biaxial load histories on thin walled tubes. The materials involved are a 2 1/4 Cr-1 Mo steel stabilized with Niobium (WN 1.6770) and a 304 stainless steel (WN 1.4948). The theoretical predictions of the plastic deformations are found to be sufficiently accurate. The evaluation of the phenomenological description for creep shows a fairly good agreement with the real creep deformation process. Special attention requires the description of softening due to microstructural changes.

Sign in / Sign up

Export Citation Format

Share Document