Nucleation kinetics, FTIR, DFT and Hirshfeld surface analysis of sodium hydrogen oxalate hydrate (NaHC2O4∙H2O) single crystal

Abstract

NaHC₂O₄∙H₂O single crystals were obtained via a low-temperature solution growth process. For recrystallization, a few excellent and faultless seed crystals were selected and a transparent single crystal of NaHC₂O₄∙H₂O measuring 18 × 10 × 5 mm³ was formed in 15 days. The extracted crystals were stable, non-hygroscopic, and had a noticeable clarity. The thermodynamics processes are examined, focusing on supersaturation, nucleation, and the size of the nucleus in the context of homogeneous nucleation. Additionally, the induction time, critical supersaturation ratio for crystallization, and the width of the metastable zone are analyzed using the solubility data of the crystallized substance. NaHC₂O₄·H₂O single crystal crystallized in triclinic crystal structure and shows a centrosymmetric space group, was recorded and analyzed using single crystal X-ray diffraction (XRD) and this crystal is one among the triclinic system. Stretching vibrations of the molecules in the NaHC₂O₄·H₂O single crystal were identified through Fourier transform infrared spectroscopy (FTIR) at different temperature (30, 100, 200, 300, 400 and 500 °C) and Fourier transform Raman spectroscopy (FT-Raman) analysis. The band structure and density of states calculations were performed using Density Functional Theory (DFT), and the energy gap was determined as 4.83 eV. The molecular interactions of the grown crystal were analyzed using Hirshfeld surface analysis. The corresponding 2D fingerprint plots have been discussed in detail to provide further insights into these interactions. The confirmation of frequency doubling from the mirror image structure is caused by the dehydration of the structural water molecules under laser irradiation and the results are detailed in the discussion sections.