Lattice Dynamics and Thermodynamic Properties of NaCrO2: An Integrated Experimental and First-Principles Study

NaCrO 2 is an indispensable compound in the separation of vanadium from chromium in high-chromium vanadium slag, highlighting the need for comprehensive thermodynamic data for this compound. In this study, a high-purity NaCrO 2 compound was synthesized by solid-state sintering. Using density functional theory (DFT) combined with experimental measurements, the lattice dynamics and thermodynamic properties of NaCrO 2 were comprehensively investigated. The phonon structure was computed using first-principles methods, and the absence of imaginary frequencies was observed, demonstrating its dynamic stability. The low-temperature heat capacity of NaCrO 2 was measured using a physical properties measurement system (PPMS). Separation of the experimental heat capacity into lattice and magnetic contributions yields a magnetic entropy of 11.30 J K −1 mol −1 , which agrees well with the theoretical spin‑only entropy of Cr 3+ ( R ln4 = 11.53 J K −1 mol −1 ). The entropy at 298.15 K is derived as 78.25 ± 0.2 J K −1 mol −1 . The DFT-calculated thermodynamic properties show good agreement with the experimental results, confirming the reliability of the computational approach. This study provides critical thermodynamic property for the NaCrO 2 in the Na 2 O–Cr 2 O 3 system, thereby directly supplementing the fundamental thermodynamic database required for the optimization of high-efficiency vanadium–chromium separation processes.