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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.
Acknowledgements
I would like to acknowledge the Referees for useful notes.