"Gold-Standard" Δ-Machine Learned Transferable Potential for Linear Alkanes

The conformational properties of linear alkanes, C_nH_2n+2, have been of intense interest for many years. Experiments and corresponding electronic structure calculations were first reported in the mid-2000s and continue to the present time. These focus on the minimum chain length where the transition from the linear minimum to the hairpin minimum occurs. We recently reported a transferable, many-body permutationally invariant polynomial (MB-PIP) potential for linear alkanes trained on roughly 253 000 B3LYP electronic energies for C₁₄H₃₀. Here we report a Δ-ML approach to elevate this B3LYP-based and a new PBE0+MBD MB-PIP potential using roughly 4500 Pair Natural Orbital Local Coupled Cluster (PNO-LCCSD(T)-F12) energies. The new Δ-corrected potentials predict the difference in these minima accurately, compared to benchmark PNO-LCCSD(T)-F12 energies results, over the range C₁₂H₂₈ to C₂₈H₅₈. Vibrational power spectra are also reported for C₁₄H₃₀ using the original B3LYP-based and Δ-ML corrected potentials. These new MB-PIP potentials for linear alkanes are the most accurate ones currently available and can be used in studies of properties of linear alkanes.