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Ultrasonic studies of the structural phase transition in squaric acid
Author(s) -
Rehwald W.,
Vonlanthen A.
Publication year - 1978
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220900106
Subject(s) - squaric acid , tricritical point , phase transition , ultrasonic sensor , critical exponent , condensed matter physics , exponent , crossover , stiffness , critical point (mathematics) , thermodynamics , materials science , phase (matter) , mathematics , physics , chemistry , mathematical analysis , phase diagram , quantum mechanics , organic chemistry , linguistics , philosophy , artificial intelligence , computer science , acoustics
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.