[CP2K-user] [CP2K:18658] Re: Ferromagnetic bulk nickel supercell optimization - multiplicity?

[GENG YUAN]

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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