[CP2K-user] [CP2K:17580] Re: SGCPMD: number of steps per SCF run increase suddenly after initial 400 MD steps

Marcella Iannuzzi marci.akira at gmail.com
Tue Aug 30 12:43:41 UTC 2022

Dear Onofrio, 

To me you system looks quite well behaved. 
The temperature is not low, maybe it helps reducing the time-step of 
activating a variable time-step, to avoid too large moves between two 
integration steps. 

On Tuesday, August 30, 2022 at 2:14:03 PM UTC+2 onofr... at gmail.com wrote:

> 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 
> follows:
> 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 
> with DO_LANGEVIN_DEFAULT F and &DEFINE_REGION. See attached 
> “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. 
> Note: 
> - 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 
> settings?
> Any help would be greatly appreciated.
> Thanks.
> Onofrio

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