  The construction of the potential energy surface (PES) of even a medium-sized
molecule employing correlated theory, such as CCSD(T), is an arduous task due
to the high computational cost. In this Letter, we report the possibility of
efficient construction of such a PES employing the molecular tailoring approach
(MTA) on off-the-shelf hardware. The full calculation (FC) as well as MTA
energies at CCSD(T)/aug-cc-pVTZ level for three test molecules, viz.
acetylacetone, N-methyacetamide, and tropolone are reported. All the MTA
energies are in excellent agreement with their FC counterparts (typical error
being sub-millihartree) with a time advantage factor of 3 to 5. The energy
barrier from the ground- to transition-state is accurately captured. Further,
the accuracy and efficiency of the MTA method for estimating energy gradients
at CCSD(T) level are demonstrated. This work brings out the possibility of the
construction of PES for large molecules using MTA with the computational
economy at a high level of theory and/or basis set.
