Iranian chemical communication 2423-4958 2 Issue 4, pp. 236-325, Serial No. 5 2014 10 01 Characterization of intermolecular interaction between Cl2 and HX (X=F, Cl and Br): An ab initio, DFT, NBO and AIM study 316 325 833 EN Morteza Vatanparast Department of Physical Chemistry, University of Tabriz, Tabriz, Iran Nabi Javadi Department of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran, Iran Rasoul Pourtaghavi Talemi Department of Chemistry, Kharazmi (Tarbiat Moallem) University, Tehran, Iran Elahe Parvini Department of Physical Chemistry, University of Tabriz, Tabriz, Iran Journal Article 2014 04 01 The character of the intermolecular interactions in Cl2-HX (X =F, Cl and Br) complexes has been investigated by means of the second-order Möller–Plesset perturbation theory (MP2) and the density functional theory (DFT) calculations. The results show that there are two types of lowest interaction potential equilibrium structures in the interactions between Cl2 and HX: X∙∙∙Cl type geometry and hydrogen-bonded geometry. The calculated interaction energies show that the X∙∙∙Cl type structures are more stable than the corresponding hydrogen-bonded structures. The nature of the intermolecular interactions has been also investigated by natural bond orbital (NBO) and atoms in molecules (AIM). The AIM analysis reveals that both types of intermolecular interactions are “closed-shell” noncovalent interactions. https://icc.journals.pnu.ac.ir/article_833_bd94bedb2d39bff8351d1968302bc58d.pdf