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Influence of temperature, pressure, magnetic field on the solid's structure by means of internal stresses

Tatyana A. Ryumshyna 1Peter Poliakov 2

1. Donetsk Physics & Technology Institute of the National Academy of Sciences of Ukraine (DonPhTI NASU), 72 R. Luxembourg St., Donetsk 83114, Ukraine
2. Physics of Mining processes Institute, Donetsk 83114, Ukraine

Abstract

In closed thermodynamics system the influence of any external thermodynamics force causes change of all thermodynamics parameters of the system [1], which within the linear approaching can be described by the generalized system of equations:
dxi =Mij dXj (1)
where dXj is the increment of thermodynamics forces (temperature, magnetic field, stress dT,dH,dσ), dxi is the change of thermodynamics parameters of system (entropy, magnetized, deformation dS,dJ,dε), and Mij is the matrix of thermodynamics coefficients, including the elastic modules of solid, coefficients of thermal expansion, magnetic receptivity, pyro- and piezomagnetic coefficients (Sλμ, αi, γik, ρi, b).
In one’s turn external influences cause the return reaction of the system. As a result own «internal thermodynamics forces» were activated in a body: internal stresses, temperature, own magnetic field. The internal stress state was selected from thermodynamic parameters as the most sensible parameter to structure of solid. Internal stresses is the integral feature of solid given by chemical bond and related to the location of electronic clouds of neighboring atoms in a lattice. These stresses are changed under external mechanical forces, heating and influence of the magnetic fields according to equation:
λ = sλμμdT + bdHk + sμvv) (2)

The value of internal stresses are enough great and achieve a few GPa (according to results [1,2]). Structural phase transition will be realized, when some critical value of internal stresses, being parameter of the material, is achieved. There are different ways to attain the critical value of stresses: by change of any parameters H, T and P according to (2) and results [1]. The analysis of experimental data [1] allowed to make a conclusion about the deciding role of internal stresses in the nature of phase transitions.

  1. P.I.Polyakov, S.S.Kucherenko. MMM, 278, (2004), p. 138-155.
  2. Table of Physical quantities. Ed.N.K.Kikoin, Moscow, (1976), -1008 p.
 

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2007, Symposium G, by Tatyana A. Ryumshyna
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-18 10:35
Revised:   2009-06-07 00:44