Pressure dependence of the Raman modes for orthorhombic and monoclinic phases of CsPbI3 at room temperature

Abstract

Metal halide perovskites (MHPs) have attracted a great deal of scholarly attention in the last few decades due to their unique properties and potential for photovoltaic and optoelectronic applications. The mechanical and electrical properties of MHPs are substantially affected by altering pressure and/or temperature. Near the phase transition pressure, these properties alter dramatically and a discontinuity in the Raman frequencies is observed. In this study, the Raman frequencies of the modes were calculated as a function of pressure (at room temperature) through the isothermal mode Grüneisen parameter for these modes by using the experimental volume data from the literature for CsPbI3. Moreover, I calculated the isothermal compressibility and the bulk modulus through the calculated Raman frequency shifts and isothermal Grüneisen parameter as a function of pressure for the orthorhombic and monoclinic phases of CsPbI3 at room temperature. The predicted Raman frequencies, isothermal Grüneisen parameter, isothermal compressibility, and the bulk modulus for the studied modes were compared with the experimental measurements below and above the orthorhombic and monoclinic phases.

First-Principles Characterization of Surface Phonons of Halide Perovskite CsPbI3 and Their Role in Stabilization

“…Raman / IR Detection of Surface Phonon Modes. Optical spectroscopies such as Raman and IR absorption are widely used for the characterization of vibrational properties, including CsPbI 3 . − Here we consider the detection of surface phonon modes using these experimental techniques. Knowing that Γ 1 and Γ 5 are IR active, and that Γ 1 , Γ 2 , Γ 3 , Γ 4 , and Γ 5 are Raman active, we tabulate the one-phonon IR/Raman activity of Γ̅-point surface modes in Table , with all Γ̅-point surface modes being Raman active.…”

Low-Temperature Heat Capacity of CsPbI3, Cs4PbI6, and Cs3Bi2I9

“…For δ-CsPbI 3 , a correction using the Grüneisen parameter and thermal expansion coefficient (eq ) is able to reproduce the heat capacity beyond Dulong-Petit fairly well. The Grüneisen parameter for this compound is reported to be 0.86 and 1.03 . Volumetric thermal expansion coefficients for δ-CsPbI 3 of (132 × 10 –6 K –1 ) and (118 × 10 –6 K –1 ) have been determined based on cell parameters in the temperature region 298–609 K as determined using synchrotron-based powder diffraction.…”

Investigation of phase transition, mechanical behavior and lattice thermal conductivity of halogen perovskites using machine learning interatomic potentials

“…The bulk modulus is a physical quantity that reflects the ability of a material to resist elastic deformation, which is defined as , where p and V are for the applied pressure and volume, respectively. 62 The relationship between the pressure and volume was called the isothermal equation of state (EOS), which was usually described by a second-order Birch–Murnaghan EOS of , where V 0 is the equilibrium volume, and K 0 is the bulk modulus at ambient pressure. 63 The larger the value, the harder the material, while the smaller the value, the softer the material.…”

“…, where p and V are for the applied pressure and volume, respectively. 62 The relationship between the pressure and volume was called the isothermal equation of state (EOS), which was usually described by a second-order Birch-Murnaghan EOS of pðVÞ ¼ 3K 0 2…”