[CP2K-user] [CP2K:18663] Re: Ferromagnetic bulk nickel supercell optimization - multiplicity?

[uca...@ucl.ac.uk]

Hi Geng,

It looks like you have already converged to around EPS_SCF 1E-7 in 32 
steps, see line: 
32 Broy./Diag. 0.10E+00   38.7     0.00000010    -43346.6332044618 -4.17E-05

Therefore I would recommend changing EPS_SCF 1E-8 -> 1E-7, and if you must 
converge to 1E-8 (generally unnecessary) then either use SCF_GUESS RESTART 
using the wavefunction file from EPS_SCF 1E-7 or try to optimise 
the BROYDEN_MIXING ALPHA and BETA values. Increasing 
the ELECTRONIC_TEMPERATURE may also help.

Best wishes,
Chris  
On Wednesday, 12 April 2023 at 22:28:35 UTC+1 GENG YUAN wrote:

> Hi Chris,
>
> I am also testing the optimization of bulk Ni using your files, which are 
> very helpful materials for me. I found that the energy converged when I 
> directly used your input file without any changes (a 5x5x5 supercell with a 
> multiplicity of 1001), but when I changed the supercell from 5x5x5 to 
> others (e.g. 4x4x4, 256 atoms total) with a modified multiplicity (256*2 +1 
> = 513), the energy couldn't converge within 500 SCF steps. I am wondering 
> what may cause this issue, and if you could share some thoughts.
>
> The only changes I made are the multiplicity and the multiple_unit_cell 
> settings, I attached my input and output files for your reference. Please 
> let me know if any concerns.
>
> Many thanks in advance,
> Sincerely,
> Geng
>
> 在2022年9月26日星期一 UTC-4 12:17:34<uca... at ucl.ac.uk> 写道：
>
> Hi Frank,
>
> I attach files where I have converged a spin moment of 0.72 in 36 SCF 
> steps for your 5x5x5 supercell.
>
> Indeed, Ni should be ferromagnetic and we can confirm this by converging a 
> solution with a multiplicity of 1 and comparing this to the ferromagnetic 
> solution with a multiplicity of 500*2+1=1001. The latter is 
> -84660.541395560532692--84661.817516270704800=1.3 Ha or 35 eV lower in 
> energy.
>
> Hope this helps,  
> Chris
>
>
>
> On Sunday, 25 September 2022 at 19:28:54 UTC+1 mdsimula... at gmail.com 
> wrote:
>
> Hello,
>
> I am attempting an optimization of bulk nickel in a 5x5x5 super cell.  
> Nickel is supposed to be ferromagnetic so I'm wondering how I set the 
> appropriate magnetization for each Ni?
>
> Based on literature, the magnetization should be ~0.64. 
>
> Do I need to set some crazy high multiplicity and the magnetization in the 
> kind section?
>
> My initial input is attached.
>
> Thanks,
> Frank
>
>

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