Profiling the binding motif between Be and Mg in the ground state via a single-reference coupled cluster method |
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Authors: | Uttam Sinha Mahapatra Debi Banerjee Rajat K Chaudhuri |
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Institution: | 1. Department of Physics, Maulana Azad College, Kolkata, India;2. Department of Physics, Shibpur Dinobundhoo Institution (College), Howrah, India;3. Indian Institute of Astrophysics, Bangalore, India |
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Abstract: | We present a study on the performance of our iterative triples correction for the coupled cluster singles and doubles excitations (CCSDT-1a+d) method for computation of potential energy surface (PES), spectroscopic constants, and vibrational spectrum for the ground state (X1Σ+) BeMg, where the ostensible inadequacy of the CCSD and CCSD(T) methods is quite expected. We compare our results with those obtained using state-of-the-art multireference configuration interaction (MRCI) investigations reported earlier by Kerkines and Nicolaides. Our estimated dissociation energy (417.37 cm?1), equilibrium distance (3.285 Å), and vibrational frequency (82.32 cm?1) are in good agreement with recent results of advanced MRCI calculations for X1Σ+ BeMg PES, which exhibits a shallow well of 469.4 cm?1 with a minimum at 3.241 Å and a harmonic vibrational frequency of 85.7 cm?1. Very weakly bound nature of X1Σ+ BeMg is clearly reflected from these values. In accord with MRCI studies, a comparison of BeMg with iso-valence weakly bound ground-state species, Be2 and Mg2, suggests that its characteristics do not exhibit any resemblance to Be2 rather, it shows a close kinship to Mg2. The agreement of our derived vibrational levels with those obtained via the high-level MRCI calculations is very encouraging reflecting the potential of the suitably modified single-reference coupled cluster (SRCC) method, CCSDT-1a+d as a tool for the study of multireference van der Waals systems. |
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Keywords: | potential energy surface spectroscopic parameters vibrational energy levels single-reference coupled cluster BeMg |
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