Τίτλος:
Hypersonic acoustic excitations in binary colloidal crystals: Big versus small hard sphere control
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
The phononic band structure of two binary colloidal crystals, at hypersonic frequencies, is studied by means of Brillouin light scattering and analyzed in conjunction with corresponding dispersion diagrams of the single colloidal crystals of the constituent particles. Besides the acoustic band of the average medium, the authors' results show the existence of narrow bands originating from resonant multipole modes of the individual particles as well as Bragg-type modes due to the (short-range) periodicity. Strong interaction, leading to the occurrence of hybridization gaps, is observed between the acoustic band and the band of quadrupole modes of the particles that occupy the largest fractional volume of the mixed crystal; the effective radius is either that of the large (in the symmetric NaCl-type crystalline phase) or the small (in the asymmetric Na Zn13 -type crystalline phase) particles. The possibility to reveal a universal behavior of the phononic band structure for different single and binary colloidal crystalline suspensions, by representing in the dispersion diagrams reduced quantities using an appropriate length scale, is discussed. © 2007 American Institute of Physics.
Συγγραφείς:
Tommaseo, G.
Petekidis, G.
Steffen, W.
Fytas, G.
Schofield, A.B.
Stefanou, N.
Περιοδικό:
The Journal of Chemical Physics
Λέξεις-κλειδιά:
Brillouin scattering; Crystalline materials; Dispersion (waves); Electric excitation; Natural frequencies; Resonance, Binary colloidal crystals; Hypersonic acoustic excitations; Hypersonic frequencies; Phononic band structures, Crystal structure
