On cubic crystal anisotropy for waves with Rayleigh-wave polarization

The anisotropy let in C-2 = [(C-11 - C-44)(2) - (C-12 + C-44)(2)]/(C11C44) for cubic crystals of the classes m3 and m3m, as well as the threshold velocity Vth, were calculated. It was found that the surface two-partial Rayleigh type waves (RTW2) cannot exist in propagation directions with values of the C-2 < - 4. It was also found that for the cubic crystals, such as RbCl, RbBr, Rbl, Li2O and KCN, there is a corresponding great positive C-2 > 5. The cubic crystal NaCN (m3m class) possesses the gigantic anisotropy term C-2 = 48.71. It was discussed that crystals with C-2 >> 1 could be suitable for investigation of possible existence of new supersonic surface waves with the phase velocity V > V-l, because the velocity V-th similar to V-l of the bulk longitudinal wave: V-l(Rbl) = 1.077Vth and V-l(Li2O) = 1.07Vth. The supersonic surface waves with V > V-l are promising, for example, for mobile communication to increase work frequency in GHz-devices, such as surface acoustical wave (SAW) filters, etc. Also, the existence condition V > V-l for the new supersonic SAW possessing the Rayleigh polarization does not obey the existence condition V < V, for the Rayleigh SAW. The phase velocity range V > V-l, in which the new SAW can be found, is separated from the one 0 < V < V, for the Rayleigh SAW by the one V, < V < V, for leaky type waves. The universal existence condition C-2 > - 1 - C-11/C-13 - 2 root C-11/C-33 for the RTW2-waves in both cubic and non-cubic crystals was also introduced. Possible applications are also discussed.