[CP2K-user] [CP2K:17579] SGCPMD: number of steps per SCF run increase suddenly after initial 400 MD steps

Onofrio Tau onofriotau at gmail.com
Tue Aug 30 12:14:03 UTC 2022

Dear CP2K community,

I have done a second-generation Car-Parrinello (SGCP) MD simulation for a 
system of 6 toluene molecules on a 4-layer Cu slab (6x6) at 900K, as 

1. the initial system (including 3 adsorbed toluene + 3 toluene in gas 
phase, see attached image) was first geometrically optimized

2. to equilibrate the geometrically-optimized system I used NVE + velocity 
rescaling looking at the conservation of temperature per region (1°region: 
Cu slab; 2°region: toluene molecules) by using the &THERMAL_REGION section 
“2_step___Equilibration” plot (4 ps of BOMD run)

3. 4 ps of sgcpMD run. I tuned GAMMA and NOISY_GAMMA per region monitoring 
again the conservation of temperature per region (see attached plot 
“3_step___sgcpMD” and text files).

However, after about the first 400 sgcpMD steps the SCF runs started to 
converge in more than 10 steps (between 11 and 16) from 3 steps, as can be 
seen in the attached .out file. I have tried different settings in the &OT 
section and I haven’t found any solution to keep the number of steps per 
SCF run small. 


- FULL_KINETIC as preconditioner seems to work better than FULL_ALL.

- every time I restart the same sgcpMD run the first SCF runs converge in 
few steps (typically 3), but then the number increase to more than 10 steps.

How to keep the number of steps per SCF run small? This behavior could be 
attributed to a bad initial geometry or exclusively to the &OT section 

Any help would be greatly appreciated.



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