On cubic crystal anisotropy for waves with Rayleigh-wave polarization

Abstract The anisotropy term C 2 = [(C 11 − C 44)2 − (C 12+C 44)2]/(C 11 C 44) 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, RbI, 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 ∼ V l of the bulk longitudinal wave: V l (RbI) = 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 t 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 t for the Rayleigh SAW by the one V t < V < V l for leaky type waves. The universal existence condition for the RTW2-waves in both cubic and non-cubic crystals was also introduced. Possible applications are also discussed. Keywords: Cubic crystalPolarizationRayleigh type waves (RTW2)AnisotropyKeywords: 43.35.Cg43.35.-c Acknowledgements I would like to acknowledge the Referees for useful notes.