Constructing Potential Energy Surface with Correlated Theory for Dipeptides Using Molecular Tailoring Approach

We demonstrate a cost‐effective alternative employing the fragment‐based molecular tailoring approach (MTA) for building the potential energy surface (PES) for two dipeptides viz. alanine‐alanine and alanine‐proline employing correlated theory, with augmented Dunning basis sets. About 1369 geometries are generated for each test dipeptide by systematically varying the dihedral angles Φ ${{\rm{\Phi }}}$ and Ψ ${{{\Psi }}}$ . These conformational geometries are partially optimized by relaxing all the other Z‐matrix parameters, fixing the values of Φ ${{\rm{\Phi }}}$ and Ψ ${{{\Psi }}}$ . The MP2 level PES is constructed from the MTA‐energies of chemically intact geometries using minimal hardware. The fidelity of MP2/aug‐cc‐pVDZ level PES is brought out by comparing it with its full calculation counterpart. Further, we bring out the power of the method by reporting the MTA‐based CCSD/aug‐cc‐pVDZ level PES for these two dipeptides containing 498 and 562 basis functions respectively. Employing a fragment‐based molecular tailoring approach, the construction of PES of dipeptides using correlated methods with the computational economy is demonstrated. The MP2/aug‐cc‐pVTZ and CCSD/aug‐cc‐pVDZ level PES are constructed for prototype dipeptides viz. alanine‐alanine and alanine‐proline.