Unveiling the Multifunctional Potential of 2D In 2 X 2 (X = S, Se, and Te) Monolayers: A First‐Principles Exploration of Electronic, Optical, Elastic, and Mechanical Anisotropy

ABSTRACT Two‐dimensional (2D) In 2 S 2 , In 2 Se 2 , and In 2 Te 2 monolayers were systematically investigated using density functional theory (DFT) calculations. Electronic structure calculations reveal indirect band gaps of 2.55 eV for In 2 S 2 , 2.44 eV for In 2 Se 2 , and 2.22 eV for In 2 Te 2 , demonstrating a systematic narrowing along the S→Se→Te sequence. Further, work functions decrease correspondingly from 6.334 to 6.047 to 5.575 eV across the S→Se→Te series. Optical analysis up to 15 eV reveals that In 2 Te 2 exhibits maximum reflectivity exceeding 0.35 at ∼4 eV, the highest refractive index (n ≈ 2.5), and the strongest plasmon‐loss peak at ∼9.5 eV, whereas In 2 S 2 achieves a maximum absorption peak at 6 eV with minimal optical losses. Elastic stiffness constants were found to decrease across the S→Se→Te order with corresponding Young's moduli of 61.90, 54.84, and 47.24 N/m, respectively. Pugh ratios of 1.61, 1.76, and 1.88, combined with Poisson's ratios of 0.23, 0.27, and 0.30, signify the brittle character of In 2 S 2, while In 2 Se 2 and In 2 Te 2 exhibit ductile behavior. In 2 S 2 , In 2 Se 2 , and In 2 Te 2 exhibit in‐plane mechanical isotropy arising from their hexagonal symmetry, confirming their suitability for flexible electronics and omnidirectional sensing applications.