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Ultrasonic studies of the structural phase transition in squaric acid

1978; Wiley; Volume: 90; Issue: 1 Linguagem: Inglês

10.1002/pssb.2220900106

1521-3951

W. Rehwald, A. Vonlanthen,

Thermodynamic properties of mixtures

Abstract The elastic stiffness functions c 11 , c 66 , c 33 , and c 44 are determined by ultrasonic velocity measurements as a function of temperature below and above the phase transition at T c = 373 K. Their variation below T c is discussed in terms of critical exponents. From their value of the order of 0.5 no unique decision can be made whether the elastic critical behaviour is determined by the crossover exponent for the stress acting as a “modifying field”, is due to a tricritical point, or is the consequence of a weakly first‐order transition.