MP2/3-21G suitability arsine reaction

2018-03-17 10:25:02

Calculating the standard free energy of formation for the arsine molecule using MP2/3-21G means many approximations are made. Considering As is a heavy atom, a basis set that is larger would be more appropriate. Also, polarization or diffusion functions can lead to better results.

However, in the case of arsine, which/what approximations would give the most severe size of error?