, where ion pairs form upon the proton transfer (PT) reaction between the Brønsted acid/base pair. Intriguing experimental observations were made for this system, including the divergent estimation of the degree of PT reaction, and the unexpected high conductivity, leads to discussion of the mechanism of proton conduction, where a Grotthus-type specific proton conduction is conjectured. For this case study, we compare the performance of PiNet and PiNet2-P3 and combine them with different reference DFT calculations. Specifically, we have used the revPBE functional 60 with Grimme's dispersion correction and the SCAN functional. A detailed description of the reference electronic structure calculations can be found in the Supporting Information. It is found that RMSEs for energy and force from PiNet2-P3/SCAN are about 11.9 meV/atom and 40.7 meV/ Å respectively, as compared to those of 7.2 meV/atom and 102.8 meV/ Å of PiNet/SCAN. A significant reduction in the force errors is also seen in the case of the revPBE-D3 functional (see Table in the Supporting Information). For the adaptive learn-on-the-fly (AcLe) task, a more critical performance metric is how well the MLPs perform on the newly sampled MD trajectories, i.e. the test error. Fig. shows that the test error of MLPs from PiNet2-P3 converge much faster as compared to ones from PiNet. In other words, it requires much less generations in the AcLe algorithm to obtain long and stable MD trajectories with PiNet2-P3. This suggests that the inclusion of P3 features helps greatly with the generalization of MLPs.