The DF-LCCSD(T0) correction of the φ/ψ force field dihedral parameters significantly influences the free energy profile of the alanine dipeptide

► Quantum chemistry DF-LCCSD(T0) level is necessary to obtain correct torsion potentials of phi/psi dihedrals of peptide backbone. ► DF-LCCSD(T) corrected force field torsion parameters can be used to generate FES of alanine dipeptide. ► FES of alanine dipeptide obtained by metadynamics is in good agreement with experimental results.