Novel rapid technique for the simulation of thermal vibration figures and diffusion routes in ionic solids

1980 ◽  
Vol 41 (C6) ◽  
pp. C6-257-C6-260
Author(s):  
M. J. Dempsey ◽  
R. Freer
Keyword(s):  
Thermal Vibration ◽  
Rapid Technique ◽  
Ionic Solids ◽  
And Diffusion

The behaviour of recoil atoms in ionic solids

1963 ◽  
Vol 272 (1348) ◽  
pp. 15-32 ◽  
Keyword(s):  
High Temperatures ◽  
Radioactive Material ◽  
High Concentration ◽  
Surface Source ◽  
Ionic Solids ◽  
Rate Of Escape ◽  
Recoil Atoms ◽  
Cation Sites ◽  
And Diffusion ◽  
Anionic Conductors

The rate of escape of thoron from solids containing radiothorium depends upon both recoil and diffusion, and is steady at any temperature if the distribution of radioactive material remains unchanged. At very high temperatures the emanating power of ThO 2 (and other indexed oxides) increases with time at constant temperature; the emanating power-temperature characteristics eventually resemble those of a solid with a surface source of thoron. The enhancement of emanating power decays with time in such a way as to prove that Th X is no longer uniformly distributed, although the distribution of the parent Rd Th is unchanged; the Th X atoms, formed by recoil from Rd Th, migrate during their lifetime to trapping sites which, in this case, are on the surface. Similar effects are found with BaThO 3 and BaF 2 , even though Th X (= Ea) can replace Ba isomorphously; these compounds are anionic conductors and have only a low concentration of vacant cation sites at high temperatures. If (e.g. in BaO) vacant sites capable of accepting large cations are present in high concentration, the recoil atoms are trapped and retained in uniform distribution.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

Ordering and diffusion in II-VI/III-VI alloys with structural vacancies

1997 ◽  
Vol 101-103 (1-2) ◽  
pp. 479-487
Author(s):  
H v. Wensierski
Keyword(s):  
And Diffusion

NMR-Study of Structure and Diffusion Processes in Li3N

1980 ◽  
Vol 41 (C6) ◽  
pp. C6-28-C6-31 ◽  
Author(s):  
R. Messer ◽  
H. Birli ◽  
K. Differt
Keyword(s):  
Diffusion Processes ◽  
Nmr Study ◽  
And Diffusion
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