[Pw_forum] CP in QE vs. CPMD from www.cpmd.org

[Axel Kohlmeyer]

On Mon, May 19, 2014 at 11:53 AM, S. Sanchez <lcqsigi at gmail.com> wrote:

> Dear Axel,
>
> Thanks again for your response. From your previous post:
>
> "in the first case you have two packages that implement first
> principles calculations using DFT and plane wave basis
> sets with pseudopotentials. due to differences in the interests
> of the developers, those two packages (quantum espresso and CPMD)
> have different strenghts and weaknesses. those can be
> mostly deduced from looking at the descriptions of the
> input file syntax (plus a few undocumented features, for
> which you have to read the source code ;-) )."
>
> My question is then, where can I find information about the strenghts and
> weaknesses of the CP.x code vs. the CPMD code (www.cpmd.org)? As you
> mentioned, one can deduce them form the input files and some undocumented
> features; this requires both to download the packages and to potentially
> run some test cases; but before doing, I would want to know, if essentially
> both codes have the same implementation as related to molecular dynamics
> calculations using DFT and plane wave basis sets, and perhaps, the only
> difference is that the CPMD code (www.cpmd.org) can deal with a large
> number of atoms and/or carry out TD-DFT tasks, etc? I don't seem to find a
> lot of information regarding this particular issue, but if the
> pw_scf community is aware of these differences, perhaps I can take
> advantage of that and narrow my search.
>

sorry, there is no alternative to making tests. there is no single answer
that applies to every case. apart from supporting a different set of
features, most of the differences are minor and whether they matter a lot
depends very much on the application at hand, size of the problem, and
requirements to pseudopotentials and alike. differences appear at every
level (features, DFT support, performance, generality of the
implementation, usability of the code, parallel efficiency), so there is no
simple answer. saying that both code are practically the same is just as
wrong as that they are very different. how similar or how different depends
on how you want to use them.

axel.



>
> SS
>
>
> On Mon, May 19, 2014 at 11:29 AM, Axel Kohlmeyer <akohlmey at gmail.com>wrote:
>
>>
>> On Mon, May 19, 2014 at 10:53 AM, S. Sanchez <lcqsigi at gmail.com> wrote:
>>
>>> Dear Axel,
>>>
>>> Thank you. I think, I was looking for literature information along the
>>> lines of your previous post. Check:
>>> http://qe-forge.org/pipermail/pw_forum/2007-January/080222.html
>>>
>>> Actually, if by documentation, you refer to the "user guide"; at least
>>> to my first impression, there are not many references one can use to
>>> understand the differences between one implementation and the other. Check:
>>> http://www.quantum-espresso.org/wp-content/uploads/Doc/cp_user_guide.pdf
>>>
>>
>> ​then i don't understand the question. you have to be more precise in
>> describing what *kind* of differences you are looking for. which features
>> are supported in one code or the other is what people usually base their
>> choices on and that is what i am referring to in the post you are quoting
>> as well.
>>
>> axel.​
>> ​
>>
>>
>>
>>
>>>
>>> SS
>>>
>>>
>>>
>>> On Mon, May 19, 2014 at 8:32 AM, Axel Kohlmeyer <akohlmey at gmail.com>wrote:
>>>
>>>>
>>>>
>>>>
>>>> On Mon, May 19, 2014 at 7:24 AM, S. Sanchez <lcqsigi at gmail.com> wrote:
>>>>
>>>>> CP in QE vs. CPMD from www.cpmd.org
>>>>>  Might you know where can I find technical information regarding the
>>>>> differences between the CP.x code in Quantum Espresso and that of the CPMD
>>>>> from www.cpmd.org
>>>>>
>>>>
>>>> ​in the documentation?​
>>>>
>>>>
>>>>
>>>>>  Thanks,
>>>>> SS
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Dr. Axel Kohlmeyer  akohlmey at gmail.com  http://goo.gl/1wk0
>>>> College of Science & Technology, Temple University, Philadelphia PA, USA
>>>> International Centre for Theoretical Physics, Trieste. Italy.
>>>>
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>>>
>>>
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>>
>>
>>
>> --
>> Dr. Axel Kohlmeyer  akohlmey at gmail.com  http://goo.gl/1wk0
>> College of Science & Technology, Temple University, Philadelphia PA, USA
>> International Centre for Theoretical Physics, Trieste. Italy.
>>
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>>
>
>
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-- 
Dr. Axel Kohlmeyer  akohlmey at gmail.com  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.
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