Fig. 2

Damped harmonic oscillator (DHO) model fitting of low-frequency Raman modes. a lowest soft mode at ~97 cm⁻¹ using all the active Raman modes in DHO fitting, till 600 K, it shows negligible nonlinear decrease in frequency with increase in temperature, later follows the linear behavior till first phase transition temperature and above, b 147 cm⁻¹ Raman mode shows linear temperature-dependent nature, c 169 cm⁻¹ Raman mode displays linear behavior as function of temperature, d merger of 315 and 285 cm⁻¹ modes near 600 K, e DHO fitting is used on only first five low-frequency Raman modes and their obtained data for low-frequency 96 cm⁻¹ soft mode with its fitting with modified Curie–Weiss law (solid line), and f full width at half maximum behavior of low-frequency 96 cm⁻¹ soft mode