The nucleation and surface properties of lithium carbonate were explored based on first-principles methods.

Abstract

<h4>Context</h4>Lithium carbonate (Li₂CO₃) is a pivotal raw material in the lithium industry, where its crystal morphology and size critically influence performance in energy storage and optoelectronic applications. However, at present, there is a lack of research on the change of properties during the nucleation process of Li₂CO₃, especially the evolution of interface properties in the early stage of growth, which is crucial to realize the precise control of the size and morphology of Li₂CO₃.This study investigates the nucleation behavior and layer-dependent evolution of electronic and optical properties of Li₂CO₃ thin films. We determine the critical nucleation radius for the (100) surface and demonstrate that as the film thickness increases from 1 to 6 layers, the material transitions from an indirect bandgap semiconductor to a direct bandgap semiconductor and finally exhibits metallic characteristics. The optical properties, including dielectric function and absorption, show a systematic layer dependence. These findings provide a fundamental theoretical basis for optimizing the crystallization process of Li₂CO₃.<h4>Methods</h4>All calculations were performed using first-principles density functional theory (DFT) as implemented in the CASTEP code. The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) functional was employed for exchange-correlation interactions. Ultrasoft pseudopotentials were used to describe core-valence electron interactions. A plane-wave cutoff energy of 600 eV was applied. Structural models of the (100) and (001) surfaces with 1-6 layers were constructed, and a vacuum layer of 15 Å was added to eliminate spurious interactions. The Brillouin zone was sampled using a 3 × 3 × 1 k-point mesh. Geometries were optimized using the BFGS algorithm until the convergence criteria for energy, force, stress, and displacement were met. Based on classical nucleation theory, the free energy change during nucleus formation was analyzed. Electronic properties (band structure, density of states) and optical properties (dielectric function, absorption coefficient, reflection coefficient) were subsequently calculated for the optimized structures.