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Uniaxial‐Stress Dependence of the NQR Frequency of 35 Cl in Paradichlorobenzene
Author(s) -
Zamar R. C.,
Brunetti A. H.
Publication year - 1988
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.2221500127
Subject(s) - anharmonicity , isothermal process , thermal expansion , thermodynamics , stress (linguistics) , atmospheric temperature range , crystal (programming language) , constant (computer programming) , materials science , harmonic , condensed matter physics , chemistry , physics , quantum mechanics , linguistics , philosophy , computer science , programming language
Measurements of the NQR frequency (NQRF) of the 35 Cl nucleus in single crystals of paradichlorobenzene are made as a function of isothermal uniaxial stress along several crystalline directions, in the range of 0 to 0.35 MPa, at a temperature of 0 °C. A linear and directional behaviour is observed. A theory is developed which includes the anharmonicity of the crystalline potential by means of the quasi‐harmonic approach. Starting from the Bayer‐Kushida theory an expression for the NQRF dependence with stress at constant temperature is deduced. Similarly, the first‐and second‐order derivatives with respect to the temperature at constant stress are obtained. In both the cases the derivatives are related with the Grüneisen parameters of the external modes and with the parameters which describe the thermodynamic state of the crystal (isothermal elastic constants and thermal expansion coefficients).