Griineisen parameter negative

B. Mosaic Stiffening and Temperature Evolution of the Boson Peak The Negative Griineisen Parameter An Elastic Casimir Effect ... 

We note first that not all amorphous substances actually exhibit a negative a in the experimentally probed temperature range. In such cases, it is likely that the contraction coming from those interactions in these materials is simply weaker than the regular, anharmonic lattice thermal expansion. Other contributions to the Griineisen parameter will be discussed later as well. 

The negative Griineisen parameters found from specific heat and susceptibility measurements on anomalous Yb intermetallics are consistent with the pressure-induced resistive response of these materials as well. For pressures less than 16kbar, the... 

Fig. 29. GrUneisen analysis for CeAl3 showing the measured coefficients of specific heat (upper plot), thermal expansion (middle plot) and the Griineisen parameter deduced from their ratio (lower plot). As the temperature is lowered Q approaches saturation to a value 50. Below 1 K it Crosses over to a large negative value (-200) appropriate to the ground state. Data for C(T) from Phillips et al. (1987) for p from Andres et al. (1975) and from Ribault et al. (1979).

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