[QE-users] safe to enable "k-point algorithm" in turbo_lanczos?

Thu Apr 16 11:00:41 CEST 2020

Dear Iurii, dear Oscar
Thank you for your feedback. Ok, as a summary we need a full-time PhD  
project or a very motivated post-doc but there is real hope that this  
produces a very useful tool. Not the worst start...
Best
Giuseppe

Quoting Timrov Iurii <iurii.timrov at epfl.ch>:

> Dear Giuseppe, All,
>
>
> Thank you very much for your comments!
>
>
>> 1) Do you think that further effort in the implementation of k_points
>> coupled with range-reparated (or even optimally-tuned-like) xc
>> functionals working with ACE and ecutfock in turbo_lanczos/davidson
>> might provide such a valuable tool?
>
> I think yes! But it requires time and effort. Of course, there are  
> issues as Oscar said, but I hope some solutions can be found. This  
> is an interesting problem, and definitively it would be interesting  
> to investigate it. But someone has to work full time on it, and not  
> just during evenings and/or weekends.
>
>> 2) Do you think that such kind of calculation might show (after a lot
>> of work, admittedly) a speedup, with respect to a GW-BSE calculation
>> of the same system, so spectacular that the juice is worth the squeeze?
>
>
> I believe that yes. In fact, in the past I worked on TDDFT-EELS with  
> (screened) hybrids and some preliminary results were very promising  
> (but I did not finish that project due to lack of time and higher  
> priority of other projects).
>
>
> Best wishes,
>
> Iurii
>
>
> --
> Dr. Iurii Timrov
> Postdoctoral Researcher
> STI - IMX - THEOS and NCCR - MARVEL
> Swiss Federal Institute of Technology Lausanne (EPFL)
> CH-1015 Lausanne, Switzerland
> +41 21 69 34 881
> http://people.epfl.ch/265334
> ________________________________
> From: users <users-bounces at lists.quantum-espresso.org> on behalf of  
> Oscar Baseggio <obaseggi at sissa.it>
> Sent: Thursday, April 16, 2020 8:59:36 AM
> To: Quantum ESPRESSO users Forum
> Subject: Re: [QE-users] safe to enable "k-point algorithm" in turbo_lanczos?
>
> Dear Giuseppe,
> I think that I could answer to the first question.
> In linear response the exx integral are different respect with to ground
> state calculation, because they contain the response wavefunction, so
> you need three different ACE operators (without response wfc, with
> response wfc, with conjugate response wfc); I’m not sure that it is
> convenient. Second problem, we have to think back an another algorithm
> to introduce the self-consisted cycle for ACE operator.
>
> But if you have some suggestions, we can call each other.
> Best regards,
>
> Oscar Baseggio
>
>
>
> Il 2020-04-15 23:59 Giuseppe Mattioli ha scritto:
>> Dear Iurii
>> The "TDDFT-solid state affair" seems to periodically resurface from
>> deep waters... Most of it started (at least for me) from a 2008 paper
>> by Izmaylov&Scuseria (J. Chem. Phys. 2008, 129, 034101) in which some
>> assumptions on the usage of range-separated functionals such as HSE
>> were made on the grounds of theory and of a (cumbersome...) example of
>>  an H chain. There is now a vast literature on the tailoring of
>> appropriated range-separated hybrid functionals for solid-state TDDFT,
>>  because we are stubborn and do not basically cope with the fact that
>> you can do (almost) whatever you want with TDDFT in the case of 0D
>> system, and that all these wonderful things are reduced to some sort
>> of poor "joint density of states" in the case of 3D systems! :-D
>>
>> I would be very happy to read a comment from you: after years of
>> painful applications of EXX to QE calculations, which I've pioneered,
>> with ACE and ecutfock we have now found a very honorable balance
>> between speed and accuracy of ground state calculations (with NC PPs,
>> in my experience, but this is another matter). The quest for a
>> possible missing rung of the Jacob's excited-state ladder between
>> epsilon.x and GW-BSE might be at hand. Thus:
>>
>> 1) Do you think that further effort in the implementation of k_points
>> coupled with range-reparated (or even optimally-tuned-like) xc
>> functionals working with ACE and ecutfock in turbo_lanczos/davidson
>> might provide such a valuable tool?
>>
>> 2) Do you think that such kind of calculation might show (after a lot
>> of work, admittedly) a speedup, with respect to a GW-BSE calculation
>> of the same system, so spectacular that the juice is worth the
>> squeeze?
>>
>> Thanks in advance to you and to everybody for any feedback
>> Giuseppe
>>
>> Quoting Timrov Iurii <iurii.timrov at epfl.ch>:
>>
>>> Dear Michal,
>>>
>>>
>>>> @Iurii: the motivation (or rather - hope) is that TDDFT (or
>>>> perhaps even epsilon.x) will give us the correct trend, whilst being
>>>> much cheaper than GW/BSE (which we are trying as well).
>>>
>>>
>>> You can try to use the turboEELS code with a very small transferred
>>> momentum q. The code prints at the end the loss function
>>> -Im[1/eps(w,q)] but also Im[eps(w,q)]. In the long wavelength limit
>>> Im[eps(w,q->0)] gives you the optical absorption spectrum at the
>>> TDDFT level in the adiabatic approximation with a LDA/GGA functional
>>> (see e.g. Fig. 3 in Comput. Phys. Commun. 196, 460 (2015)).
>>>
>>>
>>> Best,
>>>
>>> Iurii
>>>
>>>
>>> --
>>> Dr. Iurii Timrov
>>> Postdoctoral Researcher
>>> STI - IMX - THEOS and NCCR - MARVEL
>>> Swiss Federal Institute of Technology Lausanne (EPFL)
>>> CH-1015 Lausanne, Switzerland
>>> +41 21 69 34 881
>>> http://people.epfl.ch/265334
>>> ________________________________
>>> From: users <users-bounces at lists.quantum-espresso.org> on behalf of
>>> Michal Krompiec <michal.krompiec at gmail.com>
>>> Sent: Wednesday, April 15, 2020 7:54:32 PM
>>> To: Quantum ESPRESSO users Forum
>>> Subject: Re: [QE-users] safe to enable "k-point algorithm" in
>>> turbo_lanczos?
>>>
>>> Dear Oleksandr, Dear Iurii,
>>> Thank you very much, I understand that this code should rather stay
>>> disabled. @Iurii: the motivation (or rather - hope) is that TDDFT (or
>>> perhaps even epsilon.x) will give us the correct trend, whilst being
>>> much cheaper than GW/BSE (which we are trying as well).
>>> Best,
>>> Michal
>>>
>>> On Wed, 15 Apr 2020 at 18:39, Oleksandr Motornyi
>>> <oleksandr.motornyi at polytechnique.edu> wrote:
>>>>
>>>> Dear Michal,
>>>>
>>>>
>>>> The k-points algorithm of turbo_lanczos.x as it is does not give  the
>>>> correct results if there is more than one single k-point.  However
>>>> you can look up the Lanczos implementation in the thermo_pw  module,
>>>> which works fine with k-points as far as I remember (of  course bare
>>>> in mind what Iurii said about Adiabatic TDDFT).
>>>>
>>>>
>>>> Regards,
>>>>
>>>> Oleksandr
>>>>
>>>> On 15/04/2020 19:35, Timrov Iurii wrote:
>>>>
>>>> Dear Michal,
>>>>
>>>>
>>>> The k-points implementation of turbo_lanczos.x was not tested and
>>>> hence it is disabled. But most importantly, very likely there are
>>>> bugs (I think I know a few). Someone has to work on it and fix  bugs.
>>>> But is there a motivation to do so? Adiabatic TDDFT with  LDA/GGA is
>>>> known to be not accurate for the optical absorption  spectroscopy of
>>>> solids.
>>>>
>>>>
>>>> Greetings,
>>>>
>>>> Iurii
>>>>
>>>>
>>>> --
>>>> Dr. Iurii Timrov
>>>> Postdoctoral Researcher
>>>> STI - IMX - THEOS and NCCR - MARVEL
>>>> Swiss Federal Institute of Technology Lausanne (EPFL)
>>>> CH-1015 Lausanne, Switzerland
>>>> +41 21 69 34 881
>>>> http://people.epfl.ch/265334
>>>> ________________________________
>>>> From: users <users-bounces at lists.quantum-espresso.org> on behalf of
>>>> Michal Krompiec <michal.krompiec at gmail.com>
>>>> Sent: Wednesday, April 15, 2020 7:26:09 PM
>>>> To: Quantum Espresso users Forum
>>>> Subject: [QE-users] safe to enable "k-point algorithm" in
>>>> turbo_lanczos?
>>>>
>>>> Hello,
>>>> I'm trying to compute the spectrum of a crystalline insulator using
>>>> turbo_lanczos. I got the following error:
>>>>
>>>>      Error in routine lr_readin (1):
>>>>      k-point algorithm is not tested yet
>>>>
>>>>
>>>>
>>>> I guess I could just comment line 477 out in TDDFPT/src/lr_readin.f90
>>>> to disable this error:
>>>>
>>>>        ! K-points are implemented but still unsupported (use at  your
>>>> own risk!)
>>>>        !
>>>>        IF (.NOT. gamma_only ) CALL errore('lr_readin', 'k-point
>>>> algorithm is not tested yet',1)
>>>>
>>>> But how unstable is this code? Any reason not to try this?
>>>>
>>>> Thanks,
>>>>
>>>> Michal Krompiec
>>>> Merck KGaA
>>>> _______________________________________________
>>>> Quantum ESPRESSO is supported by MaX
>>>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>>)
>>>> users mailing list users at lists.quantum-espresso.org
>>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>>>
>>>> _______________________________________________
>>>> Quantum ESPRESSO is supported by MaX
>>>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>>)
>>>> users mailing list users at lists.quantum-espresso.org
>>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>>>
>>>> --
>>>> Oleksandr Motornyi
>>>> PhD candidate
>>>>
>>>> Laboratoire de Solides Irradies
>>>> Ecole Polytechnique (Palaiseau, France)
>>>>
>>>> _______________________________________________
>>>> Quantum ESPRESSO is supported by MaX
>>>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>>)
>>>> users mailing list users at lists.quantum-espresso.org
>>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>> _______________________________________________
>>> Quantum ESPRESSO is supported by MaX
>>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>>)
>>> users mailing list users at lists.quantum-espresso.org
>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>
>>
>>
>> GIUSEPPE MATTIOLI
>> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
>> Via Salaria Km 29,300 - C.P. 10
>> I-00015 - Monterotondo Scalo (RM)
>> Mob (*preferred*) +39 373 7305625
>> Tel + 39 06 90672342 - Fax +39 06 90672316
>> E-mail: <giuseppe.mattioli at ism.cnr.it>
>>
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX
>> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
>> users mailing list users at lists.quantum-espresso.org
>> https://lists.quantum-espresso.org/mailman/listinfo/users
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX  
> (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users

GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.mattioli at ism.cnr.it>