Diffusivity calculation problem

Hello,

  I try to simulation diffusivity of water in LTA zeolite. I use two ways to do my jobs.

1. using Adsorption Locator module, fill 10 water into the zeolite unit cell, and forcite module, molecular dynamic to simulate and analysis MSD profile

2. using Sorption module, Fixed loading with 10 water in LTA zeolite, other same as above

But the result is quite different, I combine the results from two approach, but  I am not sure which one is reasonable? And what's difference between them?

 

MSD.JPG