The parameters of SCREENING

eft rsd rashe... at
Tue Dec 8 17:50:18 UTC 2015

Hi Huan,

I just started searching for an answer to your same question! I found this 
link that might help both of us :)!topic/cp2k/GVnd7pmdOo4

On Tuesday, January 27, 2015 at 1:04:04 PM UTC, hua... at 
> Dear CP2K developers and users,
> I have a question on the parameters of SCREENING keyword. 
> Recently, I read the reference "*Ab initio molecular dynamics using 
> hybrid density functionals.  J. Chem. Phys., 128 (21), 214104 (2008)*". 
> The authors tested three parameters when performing the SCREENING, e.g. 
> epsilon_Schwarz, epsilon_Box and epsilon_Storage, and showed in the Table 
> III that by using the epsilong_Storage = 1/10*epsilon_Schwarz, both CPU 
> time and the RAM consumption reduced about 2-times, while retained the 
> similar accuracy. The epsilon_Box parameter seems do not significantly 
> improve the performances. 
> However, in CP2K manual, the SCREENING section lists following 5 keywords. 
> Only the first one, EPS_SCHWARZ, seems related to the epsilon_Schwarz in 
> the reference. *What the relationship between the EPS_SCHWARZ and 
> EPS_SCF? Shall I set the same value for them?*
> I am also not very clear about the rest keywords. Does the 
> SCREEN_ON_INITIAL_P and SCREEN_P_FORCES corresponding to the post-GGA 
> screening in the reference? *Shall I set them as TRUE*, if I read the 
> wavefunction_restart files? 
> If the SCREEN_P_FORCES is set to TRUE, the EPS_SCHWARZ_FORCES should be 
> specified, as the CP2K manual instructed. Then *shall I set the value 
> of EPS_SCHWARZ_FORCES equals to the value of EPS_SCF*? 
> The most important parameter, I think, is the epsilon_Storage, which does 
> not shown in the SCREENING section. Is it the keyword of 
> EPS_STORAGE_SCALING in MEMORY section? The explanation for this key word 
> is "*Scaling factor to scale eps_schwarz. Storage threshold for 
> compression will be EPS_SCHWARZ * EPS_STORAGE_SCALING*". I am not 
> sure about the relationship between this expression and the memory usage. *How 
> to set the appropriate value of memory*? 
> I would greatly appreciate it if any of you kindly give me some suggestion.
> Regards, 
> Huan
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