Benchmarking Density Functional Theory Methods for Proton Affinity Calculations of Amines
نویسندگان
1 Department of Chemistry, Faculty of Science, Imam Khomeini International University, 34148-96818 Qazvin, Iran.
2 Department of Chemistry, Faculty of Science, Imam Khomeini International University, 34148-96818 Qazvin, Iran.
doi
10.22036/pcr.2025.549429.2755چکیده
Proton affinities (PAs) of selected amines were calculated using ten density functionals combined with four Pople-style basis sets and the Def2-TZVP basis set. Increasing valence splitting from 6-31G(d) to 6-311G(d) resulted in a modest reduction in mean unsigned error (MUE), while inclusion of diffuse functions led to more substantial accuracy gains. With 6-311+G(d), M06-HF and B3LYP-D3 yielded the lowest MUE values. The Def2-TZVP basis set produced comparable performance to 6-311+G(d) based on MUE and standard deviation (SD). Both basis sets identified similar trends in functional performance, with CAM-B3LYP and M06-2X yielding the largest negative deviations from experimental values, whereas ωB97X-D demonstrates the greatest overestimation. Across them, B3LYP-D3, M06-HF, and ωB97X exhibited the lowest deviations (≤ 4 kJ mol-1), while CAM-B3LYP, ωB97X-D, and M06-2X showed higher MUEs but still below 10 kJ mol-1. Using the def2-TZVP basis set, M06-HF, B3LYP-D3, and the widely used B3LYP functional yielded PA values with accuracy comparable to that of G4MP2.
