[CP2K-user] [CP2K:18172] Re: CELL_OPT

[Marcella Iannuzzi]

Hi ?

If energy and internal pressure are slowly converging to a minimum, 
probably you need to run more iterations
Regards
Marcella

On Saturday, December 10, 2022 at 12:36:45 PM UTC+1 alberto wrote:

> Hello cp2k users,
> I want to study a crystal of YAG (Y3Al5O12) doped with Yb3 +.
>
> The cation Yb(III) tends to replace Y(III), since the two cations have 
> very similar ionic radii.
> Hence Yb (III)   occupies the dodecahedral sites of the crystal.
> However, in the scientific literature it is hypothesized that a small 
> percentage of doping Yb(III)   can occupy the octahedral sites, i.e. 
> Yb(III)   replaces Al(III)   cations.
> This hypothesis is supported by recent spectroscopic evidence. The 
> experimental data are present in the article 
> https://doi.org/10.1016/j.jssc.2022.123577
>
> To simulate the distortions of the structure when Yb(III) occupies an 
> octahedral site I started from the YAG cubic cell containing 160 atoms and 
> replaced an octahedral Al(III) with Yb(III).
>
> I managed to optimize the structure with the LDA functional, while with 
> the PBE functional after 53 cycles the calculation did not converge.
>
> I would like to optimize the structure with PBE to subsequently perform a 
> pDos calculation and find the splitting of the 4f orbitals of Yb(III) when 
> it is in the octahedral site and see if they are comparable with those 
> shown in the image below
> [image: Yb_YAG_splitting_orbitals.jpg]
> What can I improve in the input or what is wrong??
>
> I share input and post the final part of output (file too big)
>
>  
>
>  !-----------------------------------------------------------------------------!
>
>  ENERGY| Total FORCE_EVAL ( QS ) energy [a.u.]:           
>  -2786.715103466123765
>
>  ENERGY| Total FORCE_EVAL ( QS ) energy [a.u.]:           
>  -2786.715103466123765
>
>  --------  Informations at step =    55 ------------
>   Optimization Method        =                 BFGS
>   Total Energy               =     -2786.7151034661
>   Internal Pressure [bar]    =      -804.8902015897
>   Real energy change         =        -0.0000086535
>   Predicted change in energy =        -0.0000022936
>   Scaling factor             =         0.0309001301
>   Step size                  =         0.0011175379
>   Trust radius               =         0.4724315332
>   Decrease in energy         =                   NO
>   Used time                  =             1219.940
>
>   Convergence check :
>   Max. step size             =         0.0011175379
>   Conv. limit for step size  =         0.0030000000
>   Convergence in step size   =                  YES
>   RMS step size              =         0.0001385820
>   Conv. limit for RMS step   =         0.0015000000
>   Convergence in RMS step    =                  YES
>   Max. gradient              =         0.0037177331
>   Conv. limit for gradients  =         0.0004500000
>   Conv. for gradients        =                   NO
>   RMS gradient               =         0.0002540531
>   Conv. limit for RMS grad.  =         0.0003000000
>   Conv. in RMS gradients     =                  YES
>   Pressure Deviation [bar]   =      -805.9034515897 <(903)%20451-5897>
>   Pressure Tolerance [bar]   =       100.0000000000
>   Conv. for  PRESSURE        =                   NO
>  ---------------------------------------------------
>  Estimated peak process memory after this step [MiB]                       
>  1354
>
> Thank you
>

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