ULTRASOUND IN CRYSTALLINE SMECTIC |
| 1 | |
| 2009 |
| SOLID-STATE PHYSICS |
| scientific article | 534.231 | ||
| 42-46 | ultrasound velocity, absorption coefficient, liquid crystals, phase transitions, dispersion |
| The temperature dependences of longitudinal ultrasound velocity and attenuation coefficient in the 3–27 MHz frequency range have been obtained near the phase transition into the smectic-B phase of pentyloxybenzylidene- hexylaniline (PBHA) at different wave vector orientations and preferred orientation direction of smectic layer normals. The experimental results have been compared with the model of hexagonal packing of molecular centres of gravity in a smectic layer. The dispersion of elastic and dissipative parameters has been found to take place in the smectic B phase. It has been shown that the ultrasound velocity increases at the temperature phase transition to the smectic B. The inverse sign of ultrasound velocity anisotropy is observed at the phase transition smectic C–smectic B. |
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