Error of MSD calcualtion


Dear sir,

i processed the above code, but the error occured as following:
“Not enough data to calculate diffusivity”
hence, what can i do to solve this error? and the length of XDATCAR equal to 59999.


this is the error

Hi Guancred,

This error arises because the length of the simulation is insufficient. In order to calculate a diffusion coefficient, the Mean Squared Displacement (MSD) of the supplied MD trajectory must i) extend past the ballistic regime and ii) Have a sufficiently large window in the diffusive regime over which the diffusion coefficient can be calculated.

Without system specific knowledge, the atomic motion in your material at the temperatures you are interested in are likely very small and result in an MSD that may not satisfy conditions (i) and/or (ii). To solve this, I’d recommend to either increase temperature or run the simulation for a much longer time (either by increasing timestep or # of steps).

Eric

Hi sir,

Thank you for your reply. Factly, the timestep for this aimd is about 60000, and the potim=2fs, whether this time scale is not enough for this diffusion process? but according to references, this time scale is suitbale