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Lattice dynamics; phase transition; soft mode; nonlinear dynamics

The dynamics of the nonlinear excitations in a two-dimensional (2D) φ⁴-diatomic lattice, with nonlinear on-site electron-phonon coupling at the polarizable ion site has been presented, without considering the self consistent phonon approximation. One of the major results obtained from our calculations is in the understanding of continuous structural phase transition, where we have obtained the minimum in soft mode frequency at a soft mode temperatureT_s (>T_c), not at critical temperatureT_c. This occurs due to the anisotropy of such 2D systems.

Nabonita D Chowdhury¹ Sankar P Sanyal¹

1. Department of Physics, C V Raman Building, Barkatullah University, Bhopal - 462 026, India

Published

November 1995

Manuscript received

23 December 1994

Manuscript revised

1 August 1995