In CNEO-DFT calculations, all hydrogen nuclei were treated quantum mechanically, and PB4F1 basis functions 145 were employed as nuclear basis functions, with no consideration for electron-proton correlation 128,146 or proton-proton correlation (or, for the deuterated cases, also no consideration of electron-deuteron, proton-deuteron, or deuteron-deuteron correlation) for most of the calculations, and only the epc17-2 electron-proton correlation functional 128 is used in the CH 4 + OH reaction. For nuclear basis functions centered on a deuteron, the exponents of the original PB4F1 basis functions were multiplied by m D /m H .