Computational investigation of dissociative electron attachment to ammonia

Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781 039, Assam, India

E-mail: msarma@iitg.ac.in

Manuscript received online 07 May 2019, revised and accepted 13 May 2019

In this paper we have studied the dissociative electron attachment (DEA) to ammonia (NH₃ ) molecule using electronic structure theory. We have optimized neutral and anionic ammonia molecules using different electronic structure methods like Hartree-Fock (HF), second order Møller-Plesset perturbation (MP2) theory and Coupled Cluster with Singles and Doubles excitations (CCSD) with different choice of basis sets. We have found that aug-cc-pVQZ basis set provided the better results among those chosen in our investigation. Using the optimized geometries of neutral and anionic NH₃ molecules, we have further computed the potential curves of neutral and anionic NH₃ molecules varying N-H bond. Results from the potential energy curves show that anionic NH₃ molecule is metastable than that of neutral NH₃ . This provides a possibility of shape resonance which further results into dissociative electron attachment process in NH₃ molecule. We have also computed transition state followed by an intrinsic reaction coordinate calculations to see the mechanism of the DEA process. Finally, we have analysed our results from the plots of singly occupied molecular orbitals (SOMOs) of reactant, transition state and product