Elastic Constants and Coefficients

The following elastic constants Cy for room temperature have been derived from ultrasound measurements by Boppart et al. [11], [12, p. 108], [13], from phonon data (neutron scattering) by Mook, Holtzberg [17], and Brillouin scattering (sound velocity difference between bulk and surface) by Barth, GCintherodt [18]. The earlier data of Ott etal. [14] for c and c 2 are calculated from the bulk modulus K = (Cn + 2ci2)/3 = 5.1 ( 510 kbar) and (c -Ci2)/2 = 5.2 (for TmSe with a = 571 A). 

The negative sign of C12 for TmSe in the intermediate valence state is attributed to the anomalous strong breathing of the Tm ion related to valence fluctuations 4f 4f 2 + e , Barth, Guntherodt [18], Boppart etal. [11]. 

---