Analysis of Uncertainty in the Calculation of Ideal-Gas Thermodynamic Properties Using the One-Dimensional Hindered Rotor (1-DHR) Model

The uncertainty analysis of the calculation of ideal-gas thermodynamic properties using the one-dimensional hindered rotor (1-DHR), which is designed for quantum chemical treatment of internal rotations, is presented. The sensitivity of ideal-gas heat capacities and entropies to the input parameters of the 1-DHR model, that is, the reduced moments of inertia and barriers to internal rotation, is analyzed and evaluated. The calculations of energy barriers to internal rotations using the B3-LYP functional coupled with six basis sets and the empirical D3 correction accounting for dispersion interactions for a set of 60 molecular structures containing internal rotation motions were also performed, compared with available experimental values, and statistically evaluated to estimate the impact of uncertainty associated with the calculated barriers to internal rotation (15% on average, underestimated in two-thirds of cases) on ideal-gas thermodynamic properties