OICC Press International Journal of Nano Dimension 2228-5059 17 1 2026 01 02 DFT Study of HCl The Clusters Under Nano Confinement of Carbon Fullerenes 10.57647/j.ijnd.2026.1701.04 EN Aruna Thaker Advanced Materials Energy Research (AMER), Physics Department, University of Mumbai, Kalina Santacruz, Mumbai, Maharashtra, India Arwa Makki Advanced Materials Energy Research (AMER), Physics Department, University of Mumbai, Kalina Santacruz, Mumbai, Maharashtra, India Dina Hajar Advanced Materials Energy Research (AMER), Physics Department, University of Mumbai, Kalina Santacruz, Mumbai, Maharashtra, India Pradip Sarawade Advanced Materials Energy Research (AMER), Physics Department, University of Mumbai, Kalina Santacruz, Mumbai, Maharashtra, India https://orcid.org/0000-0002-6067-7270 Journal Article 2026 01 02 This report reveals the geometry, vibrational properties, and molecular orbitals with HOMO-LUMO energies of HCl clusters (HCl)n=1-2 under the confinement of carbon fullerenes CN=42-52 at B3LYP  level with basis set 6-311++g(d,p). Due to the effect of the H-bond network, the variation in bond length is observed relative to the variation of diameter of carbon fullerenes from C42 to C52. Unexpectedly, the high intermolecular stretching mode (3403.96 cm-1) is observed for a shorter bond length (H-Cl =1.234 A0) under C46. The confined HCl under C52 results in high intensity (57.75 units) for stretching mode 2859.36 cm-1 with high polarity prediction but on the other hand confined HCl dimer under C44 shows the highest stretching mode in the frequency range 3000 cm-1 with compressed bond length (H-Cl=1.254 A0) which acts as an unsaturated system. For HCl, under the confinement of C52, the bond length increases up to 1.292 A0 which is quite greater than the experimental value of free HCl (1.275 A0). Exclusively the band gap energies of both the clusters (HCl)n=1-2 are also considered to study H-bond connectivity with carbon atoms by using their (HOMO-LUMO).