Diffusive motions of water molecules near 1 °C

1978 ◽  
Vol 56 (3) ◽  
pp. 373-380 ◽  
Author(s):  
J. D. Irish ◽  
W. G. Graham ◽  
P. A. Egelstaff
Keyword(s):  
Atmospheric Pressure ◽  
Rotational Diffusion ◽  
Waller Factor ◽  
Root Mean Square Amplitude ◽  
Breaking Effect ◽  
Debye Waller Factor ◽  
Effects Of Temperature ◽  
Temperature And Pressure ◽  
Breaking Time ◽  
Structure Breaking

Neutron (quasi-elastic) scattering experiments have been carried out to investigate the effects of temperature and pressure on the motion of molecules in liquid H2O. Spectra were obtained at several temperatures between −10 and +24 °C at atmospheric pressure, and also at +1 °Cand 1.42 × 108 Pa. The root-mean-square amplitude of proton motion in solid and liquid H2O at atmospheric pressure has been inferred from measurements of the Debye–Waller factor and is nearly constant at 0.07 nm for both the solid and liquid. A model in which the translational diffusion and rotational diffusion are based on Brownian motion was fitted to our data using published diffusion coefficient data. The structure breaking time was found to be very small at 1 and 10 °C. Both these conclusions are compared with those reported in several earlier papers, which gave varying results.The spectrum measured at 1.42 × 108 Pa was slightly broader than the corresponding spectrum at atmospheric pressure, probably indicating that the well-known minimum in the viscosity at this pressure is due to a structure breaking effect.

Temperature-dependent atomic B factor: an ab initio calculation

2019 ◽  
Vol 75 (4) ◽  
pp. 624-632 ◽  
Author(s):  
Cristiano Malica ◽  
Andrea Dal Corso
Keyword(s):  
Ab Initio ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Waller Factor ◽  
Temperature Dependent ◽  
Atomic Displacements ◽  
Debye Waller Factor ◽  
Diffraction Peaks ◽  
Effects Of Temperature ◽  
Quantum Espresso

The Debye–Waller factor explains the temperature dependence of the intensities of X-ray or neutron diffraction peaks. It is defined in terms of the B matrix whose elements B αβ are mean-square atomic displacements in different directions. These quantities, introduced in several contexts, account for the effects of temperature and quantum fluctuations on the lattice dynamics. This paper presents an implementation of the B factor (8π2 B αβ) in the thermo_pw software, a driver of Quantum ESPRESSO routines that provides several thermodynamic properties of materials. The B factor can be calculated from the ab initio phonon frequencies and displacements or can be estimated, although less accurately, from the elastic constants, using the Debye model. The B factors are computed for a few elemental crystals: silicon, ruthenium, magnesium and cadmium; the harmonic approximation at fixed geometry is compared with the quasi-harmonic approximation where the B factors are calculated accounting for thermal expansion. The results are compared with the available experimental data.

PRESSURE AND TEMPERATURE EFFECTS ON THE KINETICS OF THE ALKALINE FADING OF ORGANIC DYES IN AQUEOUS SOLUTION

1959 ◽  
Vol 37 (3) ◽  
pp. 599-612 ◽  
Author(s):  
David T. Y. Chen ◽  
Keith J. Laidler
Keyword(s):  
Malachite Green ◽  
Crystal Violet ◽  
Atmospheric Pressure ◽  
Organic Dyes ◽  
Back Reaction ◽  
Bromphenol Blue ◽  
Effects Of Temperature ◽  
Temperature And Pressure ◽  
Pressure And Temperature Effects ◽  
Kinetics Of

The rates of the alkaline fading of bromphenol blue, phenolphthalein, crystal violet, and malachite green have been studied from atmospheric pressure to 16,000 pounds per square inch. The rates for phenolphthalein and malachite green were also measured over a range of temperatures in order to determine the activation energies and entropies. The reactions went essentially to completion with the exception of the fading of phenolphthalein, for which the effects of temperature and pressure on the back reaction and equilibrium constant were also studied. No effect of pressure was found for the fading of crystal violet, but the reactions of the other three dyes were accelerated by pressure, so that there are negative volumes of activation. These are correlated with the entropies of activation and are interpreted in terms of the reaction mechanisms.

Study on the Shape of Occurrence and Developing of Evaporation Wave in Short Pipe

2011 ◽  
Vol 418-420 ◽  
pp. 1948-1952
Author(s):  
Wei Min Liu
Keyword(s):  
Atmospheric Pressure ◽  
Annular Flow ◽  
Flow Patterns ◽  
Bubble Flow ◽  
Fluid Temperature ◽  
Wave Fronts ◽  
Effects Of Temperature ◽  
Temperature And Pressure ◽  
Bubble Rising ◽  
Moving Speed

When liquid within short pipe is placed suddenly into low-pressure environment from an atmospheric pressure, the effects of temperature and pressure on occurrence and developing of evaporation wave are studied, the variations of flow patterns are observed. The experimental results show that flow patterns of liquid within short pipe gradually change from bubble rising to blazing bubble flow until annular flow with a decrease in initial environmental pressure. Intensity and moving speed of the evaporation wave increased with a decrease of the diameter of pipe and pressure, and an increase of the fluid temperature. The evaporation wave fronts are in a state of explosive vaporization, instantaneous propagation velocity of evaporation wave fronts is violently fluctuating.

The effect of temperature on high-resolution TEM image contrast

1995 ◽  
Vol 53 ◽  
pp. 640-641
Author(s):  
T. Geipel ◽  
W. Mader ◽  
P. Pirouz
Keyword(s):  
Form Factor ◽  
Inelastic Scattering ◽  
Accurate Method ◽  
Waller Factor ◽  
Effect Of Temperature ◽  
Specimen Thickness ◽  
Influence Of Temperature ◽  
Debye Waller Factor ◽  
Influence Of Temperature On ◽  
Atomic Form Factor

Temperature affects both elastic and inelastic scattering of electrons in a crystal. The Debye-Waller factor, B, describes the influence of temperature on the elastic scattering of electrons, whereas the imaginary part of the (complex) atomic form factor, fc = fr + ifi, describes the influence of temperature on the inelastic scattering of electrons (i.e. absorption). In HRTEM simulations, two possible ways to include absorption are: (i) an approximate method in which absorption is described by a phenomenological constant, μ, i.e. fi; - μfr, with the real part of the atomic form factor, fr, obtained from Hartree-Fock calculations, (ii) a more accurate method in which the absorptive components, fi of the atomic form factor are explicitly calculated. In this contribution, the inclusion of both the Debye-Waller factor and absorption on HRTEM images of a (Oll)-oriented GaAs crystal are presented (using the EMS software.Fig. 1 shows the the amplitudes and phases of the dominant 111 beams as a function of the specimen thickness, t, for the cases when μ = 0 (i.e. no absorption, solid line) and μ = 0.1 (with absorption, dashed line).

Palladium-catalyzed carbonylation of 1,5-cyclooctadiene. Effects of temperature and pressure

1991 ◽  
Vol 56 (3) ◽  
pp. 663-672 ◽  
Author(s):  
Curtis B. Anderson ◽  
Rade Marković
Keyword(s):  
Carbon Monoxide ◽  
Oxidative Carbonylation ◽  
Influence Of Temperature ◽  
Carbonylation Reaction ◽  
Palladium Catalyzed ◽  
Effects Of Temperature ◽  
Temperature And Pressure

The influence of temperature and carbon monoxide pressure on the course of oxidative carbonylation reaction of 1,5-cyclooctadiene in the presence of the palladium(II) salts as a catalyst, was investigated.

scholarly journals Effects of temperature and pressure on the glass transitions of plastic bonded explosives

2000 ◽  
Vol 357-358 ◽  
pp. 89-95 ◽  
Author(s):  
Mary Stinecipher Campbell ◽  
Danielle Garcia ◽  
Deanne Idar
Keyword(s):  
Glass Transitions ◽  
Effects Of Temperature ◽  
Temperature And Pressure
Sign in / Sign up

Export Citation Format

Share Document