[CP2K-user] [CP2K:20956] bulk electrolyte aimd simulation

[ll qian]

Dear Developers,

I am seeking advice regarding AIMD simulation of organic electrolyte (LIFSI 
and DME) in the bulk phase. The experimental density is 1.04 g/cm³. Below 
are the steps I have taken:

   1. Built the solution box (18.5 Å) using Material Studio.
   2. Pre-equilibrated the system using classical MD with the COMPASS III 
   force field in the NPT ensemble for 30 ns. The density is well equilibrated 
   .Exported the last frame of the MD trajectory (closest to the target 
   density of 1.04 g/cm³) to a CIF file, 
   3. ran AIMD simulations in CP2K (input file attached in the email).

After 1 ps of aimd simulation, I found that the calculated density deviates 
significantly from the equilibrated value( (18.5 Å, ~1.04 g/cm³) ). Given 
the high computational cost of AIMD, I paused the simulation to seek advice 
before proceeding further, as I am concerned that the input file or 
simulation steps might be incorrect, leading to incorrect trajectories even 
with extended simulation time.[image: 图片1.png]

   1. In the output file, the pressure control seems poor. The average 
   pressure over 1 ps is ~400 bar (set at 1 bar). How can I adjust the 
   barostat parameters to improve this? Currently, the time constant is set to 
   100 fs.
   2.  For bulk electrolyte AIMD tasks, is it appropriate to use the 
   DZVP-MOLOPT-SR-GTH basis set? Would this significantly impact the 
   coordination structure of lithium ions?
   3. What ensemble is more appropriate for AIMD simulations? I have heard 
   that due to the small number of atoms in AIMD simulations, it is reasonable 
   to run both pre-equilibration MD and AIMD in the NVT ensemble since the 
   density cannot match experimental values. Is this correct?

I would greatly appreciate any guidance on these points.


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