Semnan University Press Progress in Physics of Applied Materials 2783-4794 7 1 2027 05 01 Quantum Chemical Investigation of Structural, Spectroscopic, Electronic and Nonlinear Optical Properties of Gefitinib Using DFT 27 36 10794 10.22075/ppam.2026.40899.1215 EN Atul Kumar Shukla Department of Physics,University of Lucknow, Lucknow-226007, India Anchal Srivastava Department of Physics,University of Lucknow, Lucknow-226007, India Mritunjai Mishra Department of Physics,Siddharth University, Siddharthnagar, Uttar Pradesh, India Sunil Kumar Mishra Department of Chemistry,M. L. K. (PG) College, Balrampur, Uttar Pradesh, India Nitin Dwivedi Department of Physics,University of Lucknow, Lucknow-226007, India R K Shukla Department of Physics,University of Lucknow, Lucknow-226007, India Journal Article 2026 04 15 Gefitinib, a well-known epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor used in the treatment of non-small cell lung cancer, was investigated in this study using density   functional theory (DFT). The molecular structure was optimized at the B3LYP/6-311G(d,p) level of theory, and the absence of imaginary frequencies confirmed the stability of the optimized structure. Vibrational analysis provided detailed insight into the characteristic functional groups of the molecule. The electronic properties were analyzed using frontier molecular orbital analysis. The HOMO and LUMO energies were calculated to be −6.0734 eV and −1.8243 eV, respectively, with an energy gap of 4.2491 eV, indicating the good kinetic stability of the molecule. TD-DFT studies demonstrated a main absorption band at approximately 325 nm, which was mainly attributed to π → π* electronic transitions in the conjugated quinazoline framework. Solvent-phase analysis using the PCM model revealed a slight red shift in the absorption wavelength, confirming the effect of solvation on the electronic excitation characteristics of gefitinib. The calculated nonlinear optical parameters showed significant polarizability and first hyperpolarizability values, which can be attributed to effective intramolecular charge transfer and extended π-conjugation. https://ppam.semnan.ac.ir/article_10794_73b277c11266681122132d024f53a75b.pdf