ABSTRACT In the present paper, we aim to develop a model theory to explain experimentally observed variations of dielectric constant and dielectric loss in potassium dihydrogen phosphate (KDP) crystal. For deriving formulae for the dielectric constant, loss tangent for the KDP crystal, first we shall modify the earlier authors’ (Ganguli et al.) model Hamiltonian by adding also a third‐order phonon anharmonic interaction term, electric field term, and extra spin‐lattice interaction terms into it. We shall use the double‐time thermal green function approach to derive formulae for normal mode frequency, dielectric constant, and dielectric loss tangent. Model values will be fitted in formulae to obtain thermal variations of normal mode frequency, dielectric constant, and loss tangent for the KDP crystal. Theoretical variations will be compared with experimentally reported data of Kaminow.
Dhooma et al. (Sun,) studied this question.