CRITICAL X-RAY-SCATTERING AT THE PEIERLS TRANSITION IN THE QUASI-ONE-DIMENSIONAL SYSTEM (TASE4)(2)I

By means of high-resolution x-ray scattering, we have studied the temp erature dependence of the critical scattering associated with the Peie rls transition in (TaSe4)(2)I. From a careful intensity and line shape analysis the critical exponents beta, gamma and nu were derived. beta , gamma and nu are the critical exponents of the temperature dependenc e of the order parameter, the susceptibility and the correlation lengt h of the order parameter fluctuations, respectively. Though this incom mensurate structural phase transition is reported to be continuous, an unusual exponent value is obtained: beta approximate to 0.2. The smal l value of beta suggests a blurred first-order transition. We also rep ort on the anisotropy of the correlation in the basal plane perpendicu lar to the (TaSe4)infinity-chain direction.