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Re: [FreeON-devel] The FreeON wiki is open for business!

From: Matt Challacombe
Subject: Re: [FreeON-devel] The FreeON wiki is open for business!
Date: Thu, 03 May 2012 15:22:36 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0) Gecko/20111223 Thunderbird/10.0

Hi Gao,

We have no plans to implement frequency dependent polarizability -- this remains an open problem for O(N). We are however, ready to help anyone out there that might
want to implement that in FreeON.

For many materials, I think the w=0 (static) response is interesting, for
example in the context of thin film ultra-capcitors. In that case, I think one would at least want hybrid level of HF/DFT. As I mentioned earlier, the DFT part of response is not developed -- we have no immediate plans to develop that either
-- although we'd also be happy to help anyone interested in doing so.

Best, Matt

On 05/03/2012 03:07 PM, Gao Bin wrote:
Hi, Matt

I am really sorry that I did not find your reply ago (due to our email system 
is too smart by putting emails in the same thread together).

To be honest, previously I want to use FreeON to perform dynamic response 
calculations of periodic systems because there might be limited programs could 
do that.

But since FreeON is gamma point only and able to handle thousands of atoms, I 
need to change my idea by calculating some large systems, which I need to 
consider ...

By the way, I am sorry that I may abuse the term "dynamic response". More 
correctly, I should say I want to calculate, for instance, frequency dependent 
polarizability, hyperpolarizability. I notice FreeON does not have such functionality 
right now. But may I ask if someone will implement the frequency dependent solver in 
FreeON? Thank you.


From: address@hidden address@hidden on behalf of Matt Challacombe address@hidden
Sent: Monday, April 30, 2012 8:06 PM
To: address@hidden
Subject: Re: [FreeON-devel] The FreeON wiki is open for business!

Hi Gao,

FreeON is gamma point only, for all periodic calculations.   For
large, non-metalic and heterogeneous
systems, gamma point should converge pretty quickly with respect to N.
  If you have a small system
with lots of symmetry, well, FreeON is probably not the right tool.

While FreeON (MondoSCF) used to be fairly well parallelized with MPI,
only the NEB part over clones (beads)
is currently MPI parallel.   We dropped support for that part of the
code because (1) it was really clumsy and
difficult to support and (2) we are redoing the code from the ground
up in a different HPC paradigm.  See
for example, Nicks recent paper on SpAMM.  This will replace the BCSR
structures with quad and oct-trees
and a task parallel approach.  This will be much, much easier to
maintain and develop around (+faster).

The dynamic response is in RQI.F90 as you correctly understand. You
would probably need to implement in
both RQI.F90 and some other "backend" files.  Its important to
understand the front/back end way FreeON
is built.  It has a lot of advantages, especially for very large
systems, but can be a pain at first.  The advantage
is, if something goes wrong with ie a 2000 atom calculation, you can
for instance easily re-run/debug/profile
etc the most important/costly/buggy part of the code, instead of
starting from the beginning.
RQI is somewhat unique in that the linear algebra is in the front end,
while it makes backend calls to the J+K builds.
This is pretty different than the rest of the code.  We could probably
back end RQI, and nest the J+K builds.
We should consider that, along with ways to let some of the linear
algebra live in the front end, as it is now, but
maybe in a more friendly way.   Our task parallel approach we are
working towards will help and inform
these choices a lot.

So maybe let me know what properties you are interested in, and if HF
is going to be enough, and we can
discuss more.

Best, Matt

On Mon, Apr 30, 2012 at 11:08 AM, Gao Bin<address@hidden>  wrote:
Hi, Matt

Thank you so much for your detailed reply. I have read your paper about static 
response before :-) I will read the dynamic paper later on, thank you!

By the way, may I ask you some more questions?

(1) You said the calculations is gamma-point only for static response. Is it 
also true for dynamic response? May I ask if it is easy or not to extend FreeON 
for any reciprocal space points?

(2) If I want to calculate dynamic response, is this part of code parallelized 
using MPI over several nodes, or only on one node using shared memory (for 
instance, the matrix operations)?

(3) I have read the code, if I understand correctly, the dynamic response is 
implemented in FreeON/RQI.f90. If I am interested in how it works, or want to 
implement calculations of some new properties, should I work on FreeON/RQI.f90 
or other files? Thank you so much.


From: address@hidden address@hidden on behalf of Matt Challacombe address@hidden
Sent: Friday, April 27, 2012 8:30 PM
To: address@hidden
Cc: address@hidden
Subject: Re: [FreeON-devel] The FreeON wiki is open for business!

Hi Gao,

There are examples in the freeon/Validate directory.  For the static
response there is the
file: Validate/Response/Static/Peroxide.inp    Note that only the HF
model has been implemented
so far, and for static response, only for polarization.  Also, the
polarization will not work
properly if the chosen axis is periodic, because it is gamma-point
only  (you can do z axis
polarization in a 2D slab though, with slab along xy plane).

There is also a TDSCF directory next door to static with the file:
Validate/Response/TDSCF/C2H4.inp  Again, this is only HF (RPA), but
you can do 1000's of atoms if you like.  The ref paper for dynamic
response is here:  I can get you the papers
for static response too.  This method also works very well, ie if you have
a local excitation, like a chromophore in a protein matrix.  Then, the cost
of RPA is O(1) while cost of SCF is O(N).

I think the question for you is, will TD-HF (RPA) be enough or do you need
a DFT component?  I'm pretty sure this is the only O(N) method for TD-SCF,
so it might be worth thinking about trying to implement the DFT part.
it is a bit time consuming, and I didn't have the time to do it yet.
Maybe you can live
without it though, or maybe you or someone you know is interested in
programming it a bit (I'd be willing to help but couldnt do it all).
Also, if you need
more than the first eigenvalue, you would need to do some extra programming.
I have that working somewhere in a prototype, but not strongly implemented.

I hope that helps.

Best, Matt

On Thu, Apr 26, 2012 at 3:58 PM, Gao Bin<address@hidden>  wrote:
Hi, Nick

Thank you. Since I just started to use FreeON (indeed I am still struggling
to get it be compiled), I am afraid I could not contribute immediately, but
I will do my best :-)

Now, I am trying to use FreeON. To me, the first step is to understand the
keywords. I notice all the keywords are parsed in subroutines of FreeON
directory, but there are ParseXX.f90 and XXKeys.f90. I wonder which files I
should look into? Thank you so much.

Another question is related to the feature mentioned in wiki page "Advanced
features include O(N) static and dynamic response, as well as time
reversible Born Oppenheimer Molecular Dynamics (MD)". I am interested in
dynamic response, but I did not find any routine in FreeON/Response.f90
related to dynamic response. Did I misunderstand or did I look into a wrong
file? Moreover, may I ask what the reference papers for static and dynamic
response? I notice there are some reference papers in, but I am not sure which one and if they
are enough. Therefore, I think it would be better to put the reference list
in the current wiki page (well, just my opinion).


From: Nicolas Bock address@hidden
Sent: Wednesday, April 25, 2012 8:40 PM
To: address@hidden; freeon-devel; Gao Bin; Jose R. Valverde
Subject: The FreeON wiki is open for business!


please visit

and check out our new wiki. There is nothing really on there yet, but we are
hoping that with your help there will be soon. The wiki is completely open,
which means that you can add, edit, and delete content as you wish, with or
without a wiki account.

I suggest we think about what information a user or a developer would like
to find on a wiki. My guess is (in no particular order of importance):

* Input file syntax
* Example inputs, illustrating all features of FreeON
* A feature list

I would like to encourage you to add to this list and of course to start
adding content to the wiki.

Thanks already for your help,


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