A comparative study of the potential energy surfaces of (CO)2, CO-CS and (CS)2

The potential energy surfaces of two van der Waals complexes, namely CO-CS and (CS)(2) have been investigated and compared against the experimentally observed (CO)(2). Two stable conformers for (CO)(2) with very similar binding energies were identified, whose geometrical parameters and energetics were found to converge at CCSD(T)/CBS//MP2/aug-cc-pV5Z level. Therefore, CO-CS and (CS)(2) have also been optimized up to MP2/aug-cc-pV(5+d)Z level, where three and one stable conformers have been identified, respectively. Binding energy of (CS)(2) has been found to be over four times higher than (CO)(2). The same of CO-CS were found to lie in between that of (CO)(2) and (CS)(2). Energy decomposition analysis predicted dispersion interaction to play a major role in stabilizing the dimeric systems, its contribution increasing monotonically with decreasing binding energies. Atoms in molecule and non-covalent interaction analysis were also performed to visualize and analyze the nature of intermolecular interactions.