Accuracy of DFTB for high-T carbon chemistry: Summary
• DFTB reproduces B3LYP/6-31G(d) energetics very well
• DFTB reproduces B3LYP/6-31G(d) geometries excellently (PES is qualitatively and quantitatively correct)
• DFTB compares much better w/DFT than conventional semiempirical methods at similar computational cost
• High-level DFT may not always give the qualitatively correct answer in unusual cases, especially when ring strain is high
• Fortunately, cases where DFT fails are rare and related to extremely unlikely geometries
Approximate DFT/MD* possible over ~ ns timescale