Figure 2. The number of
permeated molecules NP versus timet through various MXenes with different nanopores. (a)
~4 Å Ti4C3 nanopores,
(b) 2.92 Å Ti4C3 nanopores, (c) enlarged
drawing of (b), (d)
~2 Å nanopores of
four kinds of MXenes. The NP ~t relationship for other kinds of MXenes with 2~4
Å nanopores are shown in Figures S1-S2 . The black dashed line
represents the fitted curve.
Currently, there are two prevailing fitting methods for calculating gas
permeance from NEMD simulations of relaxation process: exponential
fitting11, 26, 31, 52-54 and linear
fitting,55-58 see supplementary information (SI) gas
permeance calculation methods for details, yet there has been seldom
studies on whether these two methods could yield consistent results.Figure 3 shows that, the simulated permeance of He and
CH4 cross the four studied MXene nanopores with varyingd , calculated with both fitting methods well agree with each
other, with correlation coefficient (R 2) above
0.97. Further theoretical derivations (Equations S7-S8 in SI)
show the results calculated with these two methods should agree with
each other if the calculations are performed correctly. Thus, following
discussions would focus on gas permeance calculated from the linear
fitting method.