[CPMD-list] about oxygen Ultra-soft PP generated by USPP

[qfzhang]

Hi,
    Sorry for too many questions. I want to use US-PP in PIMD calculations, so I
 think it's much faster than the NC-PP. Is there any problem to use US-PP for PI
MD?
    And I also want to know the format of the US-PPs using in CPMD.Can you tell 
me something about that?
    
    Best wishes
                                                    Qianfan Zhang
                                                     2007-04-05
   
Axel Kohlmeyer д:

> On Mon, 2 Apr 2007, qfzhang wrote:
> 
> QZ> Hi,
> QZ>   Thanks for the reply! the input file is attached here.I use MESH 
> QZ> and DUAL, and
> 
> why MESH???
> 
> QZ> calculate a charged system. Is there some other keyword that 
> QZ> should be specified?
> 
> QZ>  I have tried to add l=2 to generate O US-PP.But it shows that 
> QZ>  \\' no tuning point fot state nnlz = 320 on iteration 1\\' what\\'s
> QZ> wrong with it? The files were also attached here.
> 
> as i was alluding to in the previous mail. this state is not bound.
> please check the literature on generating pseudopotentials...
> 
> QZ>    Another question is can I use UPF US-PP? I see there are UPF
> QZ> US-PP on the web page of PWscf.How can I change them between the
> QZ> UPF\\'s and FORMATTED\\'s?
> 
> there is no conversion between UPF and native uspp.
> anyways, i would actually primarily suspect the Zr and Ba
> pseudopotentials. the parameter set shipped with the vdb
> code was seemingly tuned for an older version of the code
> which had a different fitting algorithm. with the current
> code you get (unphysical) negative densities for both of them,
> so i would suspect _them_ before i suspect the d-channel of 
> the oxygen having an impact.
> 
> cheers,
>    axel.
>    
>    Best wishes
>                                                      Qianfan Zhang  
> Axel Kohlmeyer ??:
> 
>> On Mon, 2 Apr 2007, qfzhang wrote:
>> 
>> QZ> Hi, dear all!
>> 
>> dear qianfan zhang.
>> 
>> QZ>   I want to use USPP to generate the US-PP for oxygen in the
>> QZ> calculation of oxi de. But the result is not good in the oxide(even
>> QZ> I use very large supercell). I want to add l=2 channel in the O
>> 
>> first of all, if you don\\\'t tell us, what you are trying to do and
>> what your input looks like, i would strongly suspect that you are
>> doing something wrong, since the oxygen ultrasofts generated by 
>> bernd meyer _do_ work well with a large number of systems, even
>> oxides. so please provide some input that _proves_ that the 
>> pseudopotential is at fault. thanks.
>> 
>> QZ> US-PP, because I find that the TM-PP I used bef ore includes the d
>> QZ> channel.  But I find it is impossible for me to generate such a
>> 
>> you should be _very_ careful with that. pseudopotentials created
>> with the \\\'haman\\\' style PP code that are in the cpmd pp library
>> mostly contain a unbound, bogus d channel, which will either have
>> little contribution (if used with LMAX=D LOC=P) or may give worse
>> results (if used with LMAX=D, which implies LOC=D).
>> 
>> QZ> US-PP.Is there anyone who know how to do that?
>> 
>> adding another projector to existing USPP inputs is actually
>> rather straightforward. just follow the instructions in the 
>> INPUT_XX files that ship with the code. the problem is to have 
>> it converged and bound. so you may have to slightly oxidize
>> the atom and/or shift some fractional occupation to the d-state.
>> 
>> QZ>   Or who know some tricks to improve the quality of US-PP?
>> 
>> before you put too much effort into optimizating the potential,
>> you may be better off to stick with a reasonable norm-conserving
>> pseudopotential. you avoid some of the overhead and \\\'only\\\' need
>> some more cpus resources to distribute the work. but then again
>> with ultra-softs, CPMD usually does not scale that far, so in case
>> you have a large enough resource to run on, you may find NC-PPs 
>> about as efficient as US-PPs.
>> 
>> cheers,
>>    axel.
>> 
>> 
>>  
>>    Best wishes
>>                                                       Qianfan Zhang
>>                                                       2007-04-02
>> 
>> 
>> 
>> -- 
>> =======================================================================
>> Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
>>    Center for Molecular Modeling   --   University of Pennsylvania
>> Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
>> tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
>> =======================================================================
>> If you make something idiot-proof, the universe creates a better idiot.
>> 
> 
> 
> 
> 
> -- 
> =======================================================================
> Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
>    Center for Molecular Modeling   --   University of Pennsylvania
> Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
> tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
> =======================================================================
> If you make something idiot-proof, the universe creates a better idiot.
>