Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Weiss theory

The calculated energy of interaction of an atomic moment and the Weiss field (0.26 uncoupled conduction electrons per atom) for magnetic saturation is 0.135 ev, or 3070 cal. mole-1. According to the Weiss theory the Curie temperature is equal to this energy of interaction divided by 3k, where k is Boltzmann s constant. The effect of spatial quantization of the atomic moment, with spin quantum number S, is to introduce the factor (S + 1)/S that is, the Curie temperature is equal to nt S + l)/3Sk. For iron, with 5 = 1, the predicted value for the Curie constant is 1350°K, in rough agreement with the experimental value, 1043°K. [Pg.762]

The main alternative to the modified Haber-Weiss theory is a two-equivalent oxidation of Fe by peroxide , viz. [Pg.460]

A. A. Maradudin, E. W. Montroll and G. H. Weiss, Theory of Lattice Dynamics in the Harmonic Approximation, Academic, New York, 1963. [Pg.150]

At the Curie point, the Weiss theory predicts that for T > Te, in the absence of an external field, the spin order vanishes completely. Actually there is considerable short-range order just above Te, as has been verified by neutron diffraction experiments (405,675). It is the problem of short-range order that is tackled by the more exact quantum statistics mentioned in connection with equation 94. At very high temperatures (T Te), there is no short-range order, and the experimental curve approaches the Curie-Weiss curve asymptotically. Theory shows that the possibility of short-range ordering lowers the... [Pg.85]

Therefore, in this treatment of the equatkm, the Weiss theory gives the secondnirder transition. The transition point T, is given by... [Pg.156]

The second-order ferroelectric transitions can be modeled using the Curie-Weiss theory of ferromagnetism. It is assumed that there is a local field that is proportional to the polarization or E-Loc = E + yP/so, where y is the constant of proportionality. For T>Tq, Equation 23.28 gives P = Np Eux /kT and the susceptibility is given by... [Pg.455]

The Weiss theory has been refined and verified experimentally in several papers, in which expressions are usiially derived for the equilibrium potential (Eg) of the O2 — H2O2 system. This last question is discussed in [17]. The basis used for the discussion was the... [Pg.414]

The strongest argument in favor of the Weiss theory is the result from comparison of the exchange current and oxygen evolution rate (v)... [Pg.418]

See other pages where Weiss theory is mentioned: [Pg.481]    [Pg.85]    [Pg.341]    [Pg.655]    [Pg.208]    [Pg.221]    [Pg.193]    [Pg.238]    [Pg.1550]    [Pg.2039]    [Pg.94]    [Pg.155]    [Pg.157]    [Pg.500]    [Pg.286]   
See also in sourсe #XX -- [ Pg.286 ]



SEARCH



Curie-Weiss Theory (Classical Approach)

Curie-Weiss theory

Weiss Field Theory

© 2024 chempedia.info