X-ray structural investigations of the phase transition in benzyl crystals

The Bragg (fundamental) and diffuse reflections from the M-points of the Brillouin zone boundary of the paraphase of the benzyl crystals, whose integrated intensity is related to the order parameter and its fluctuations, respectively, have been investigated. The original information on the temperature behavior of the order parameter and the diffuse scattering is obtained and the values of the corresponding critical exponents are determined. The temperature behavior of the correlation radius and its anisotropy are analyzed. The conclusion is drawn that the phase transition in these crystals is close to the tricritical point. The mechanism of the phase transition in the benzyl crystals alternative to the "trigger" mechanism is suggested.