From owner-chemistry@ccl.net Thu Jan 26 13:19:00 2017 From: "Thomas Manz thomasamanz_._gmail.com" To: CCL Subject: CCL: interesting article in Science on DFT Message-Id: <-52612-170126131652-19009-faFKenc46c8iSyIA2V5Jyw.:.server.ccl.net> X-Original-From: Thomas Manz Content-Type: multipart/alternative; boundary=001a114136dafa605b05470359c9 Date: Thu, 26 Jan 2017 11:16:43 -0700 MIME-Version: 1.0 Sent to CCL by: Thomas Manz [thomasamanz ~ gmail.com] --001a114136dafa605b05470359c9 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable A recent issue of Science contained an interesting article "Density functional theory is straying from the path toward the exact functional"[1]. I agree with the article's main idea that new DFT functional development should focus on both reproducing the energies and the electron densities. I also agree with the article's statement that one should be cautious to make sure new functionals obey appropriate limits and norms without using an excessive number of empirically fitted parameters. However, there is a notable limitation in their methodology. Specifically, in the article they claim that "The results for molecules would be ambiguous because for typical approximate functionals, accurate molecular energies and densities arise only from an understood but uncontrollable error cancellation between a functional=E2=80=99s exchange and correlation components" I do not agree with this, because many energetic properties of molecules have been measured unambiguously using spectroscopic techniques. Also, it is possible to unambiguously compute the energy and geometry that is theoretically predicted by each functional for a chosen molecule. So, it is in fact possible to unambiguously compare theoretically computed and experimentally measured energies for molecules. Moreover, the authors used CCSD calculations as the reference data for the electron densities of single atoms, and the CCSD method can be applied to molecules not just single atoms. The authors reported the electron density errors for isolated closed-shell atoms and atomic cations only, while citing the energy errors for entirely different types of systems (i.e., the large dataset of Peverati and Truhlar [2]). While the study raises many interesting questions, it did not in fact compare the accuracy of functionals for reproducing both the energies and the electron densities of the same materials. So, any conclusions about how one functional gets the energies better but the electron densities worse are limited by the fact that those measures were quantified for entirely different classes of materials. Specifically, we do not know whether the functionals that got the energies better for molelcules performed better or worse for the electron densities of those materials, because that was never measured. Moreover, we do not know whether the functionals that performed better for the electron densities of the isolated closed-shell atoms and atomic cations performed better or worse for the energies of those materials, because that data was not reported. The study has shown is that some functionals, which perform better for electron density of one type of system have also performed worse for the energies of other types of systems. However, I think the study has serious limitations because the energies and electron densities were not compared for the same systems. Nonetheless, it raises some interesting questions that should be explored in future studies. Specifically, do the recent functionals that perform well for molecules and solids get the electron density distributions for those materials more or less accurately than the earlier functionals? [1] M. G. Medvedev, I. S. Bushmarinov, J. Sun, J. P. Perdew, and K. A. Lyssenko, Science 355 (2017) aah5975. [2] R. Peverati, D. G. Truhlar, Philos. Trans. R. Soc. A 372 (2014) 20120476. Tom --001a114136dafa605b05470359c9 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
A recent issue of Science contained an interesting article= "Density functional theory is
straying from the path toward the e= xact functional"[1].

I agree with the article= 's main idea that new DFT functional development should focus on both r= eproducing the energies and the electron densities. I also agree with the a= rticle's statement that one should be cautious to make sure new functio= nals obey appropriate limits and norms without using an excessive number of= empirically fitted parameters.

However, there is = a notable limitation in their methodology. Specifically, in the article the= y claim that "The results for molecules would be ambiguous because for= typical approximate functionals, accurate molecular energies and densities= arise only from an understood but uncontrollable error cancellation betwee= n a functional=E2=80=99s exchange and correlation components" I do not= agree with this, because many energetic properties of molecules have been = measured unambiguously using spectroscopic techniques. Also, it is possible= to unambiguously compute the energy and geometry that is theoretically pre= dicted by each functional for a chosen molecule. So, it is in fact possible= to unambiguously compare theoretically computed and experimentally measure= d energies for molecules. Moreover, the authors used CCSD calculations as t= he reference data for the electron densities of single atoms, and the CCSD = method can be applied to molecules not just single atoms.

The authors reported the electron density errors for isolated close= d-shell atoms and atomic cations only, while citing the energy errors for e= ntirely different types of systems (i.e., the large dataset of Peverati and= Truhlar [2]). While the study raises many interesting questions, it did no= t in fact compare the accuracy of functionals for reproducing both the ener= gies and the electron densities of the same materials. So, any conclusions = about how one functional gets the energies better but the electron densitie= s worse are limited by the fact that those measures were quantified for ent= irely different classes of materials.

Specifically= , we do not know whether the functionals that got the energies better for m= olelcules performed better or worse for the electron densities of those mat= erials, because that was never measured. Moreover, we do not know whether t= he functionals that performed better for the electron densities of the isol= ated closed-shell atoms and atomic cations performed better or worse for th= e energies of those materials, because that data was not reported.

The study has shown is that some functionals, which perfor= m better for electron density of one type of system have also performed wor= se for the energies of other types of systems. However, I think the study h= as serious limitations because the energies and electron densities were not= compared for the same systems. Nonetheless, it raises some interesting que= stions that should be explored in future studies. Specifically, do the rece= nt functionals that perform well for molecules and solids get the electron = density distributions for those materials more or less accurately than the = earlier functionals?

[1] M. G. Medvedev, I. S. Bus= hmarinov, J. Sun, J. P. Perdew, and K. A. Lyssenko, Science 355 (2017) =C2= =A0aah5975.

[2] R. Peverati, D. G. Truhlar, Philos= . Trans. R. Soc. A 372 (2014) 20120476.=C2=A0

Tom<= /div>
--001a114136dafa605b05470359c9-- From owner-chemistry@ccl.net Thu Jan 26 17:14:00 2017 From: "Susi Lehtola susi.lehtola * alumni.helsinki.fi" To: CCL Subject: CCL: interesting article in Science on DFT Message-Id: <-52613-170126165707-24114-NM+zviJIZc73rzhPZw5xfg%server.ccl.net> X-Original-From: Susi Lehtola Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=utf-8; format=flowed Date: Thu, 26 Jan 2017 13:56:53 -0800 MIME-Version: 1.0 Sent to CCL by: Susi Lehtola [susi.lehtola---alumni.helsinki.fi] On 01/26/2017 10:16 AM, Thomas Manz thomasamanz_._gmail.com wrote: > A recent issue of Science contained an interesting article "Density > functional theory is > straying from the path toward the exact functional"[1]. This has already been discussed on the list in the thread "DFT discovers it's recapitulating QSAR" I'd like to repeat my arguments in http://www.ccl.net/cgi-bin/ccl/message-new?2017+01+06+006 that you could rewrite the result of the study as a much less catching "Minnesota functionals fail to reproduce electron density in small atoms and cations" -- ----------------------------------------------------------------------- Mr. Susi Lehtola, PhD Chemist Postdoctoral Fellow susi.lehtola-x-alumni.helsinki.fi Lawrence Berkeley National Laboratory http://www.helsinki.fi/~jzlehtol USA ----------------------------------------------------------------------- From owner-chemistry@ccl.net Thu Jan 26 23:16:01 2017 From: "Thomas Manz thomasamanz|a|gmail.com" To: CCL Subject: CCL: interesting article in Science on DFT Message-Id: <-52614-170126224238-1506-HyxlUMr9GwztrU6OcNDEUQ===server.ccl.net> X-Original-From: Thomas Manz Content-Type: multipart/alternative; boundary=001a113778c6768fee05470b411f Date: Thu, 26 Jan 2017 20:42:31 -0700 MIME-Version: 1.0 Sent to CCL by: Thomas Manz [thomasamanz-$-gmail.com] --001a113778c6768fee05470b411f Content-Type: text/plain; charset=UTF-8 Hi Susi, Thanks for pointing that out. I agree with many of your critiques on the Science article. It would be interesting if someone would do a more rigorous study comparing more functionals with proper comparisons of both energies and electron distributions for a diverse set of materials. One of the things that I struggle with is that with so many newly developed DFT functionals in recent years, I have no idea which of them actually perform well across diverse materials. A study that compares not only energetics, but also computed electron densities, across diverse materials (molecules, solids, transition states, etc.) could be extremely valuable for figuring out which recently developed functionals actually perform well. One of the things the Science article claims is that the recent functionals are getting worse on the electron densities, but as you have pointed out, we don't necessarily know whether this is truly the case. Particularly, because the Science article tested such a limited set of materials (i.e., single closed shell atoms and atomic cations) for the densities but cited energies for entirely different material types, and as you pointed out the functionals tested omitted many recent approaches developed by diverse research groups. It would be great if someone could do a more rigorous and inclusive study. Tom On Thu, Jan 26, 2017 at 2:56 PM, Susi Lehtola susi.lehtola * alumni.helsinki.fi wrote: > > Sent to CCL by: Susi Lehtola [susi.lehtola---alumni.helsinki.fi] > On 01/26/2017 10:16 AM, Thomas Manz thomasamanz_._gmail.com wrote: > >> A recent issue of Science contained an interesting article "Density >> functional theory is >> straying from the path toward the exact functional"[1]. >> > > This has already been discussed on the list in the thread > "DFT discovers it's recapitulating QSAR" > > I'd like to repeat my arguments in > http://www.ccl.net/cgi-bin/ccl/message-new?2017+01+06+006 > > that you could rewrite the result of the study as a much less catching > "Minnesota functionals fail to reproduce electron density in small atoms > and cations" > -- > ----------------------------------------------------------------------- > Mr. Susi Lehtola, PhD Chemist Postdoctoral Fellow > susi.lehtola|-|alumni.helsinki.fi Lawrence Berkeley National Laboratory > http://www.helsinki.fi/~jzlehtol USA > -----------------------------------------------------------------------http://www.ccl.net/chemistry/sub_unsub.shtmlConferences: http://server.ccl.net/chemistr > y/announcements/conferences/> > > --001a113778c6768fee05470b411f Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Hi Susi,

Thanks for pointing that out. = I agree with many of your critiques on the Science article.
It wo= uld be interesting if someone would do a more rigorous study comparing more= functionals with proper comparisons of both energies and electron distribu= tions for a diverse set of materials.
One of the things that I st= ruggle with is that with so many newly developed DFT functionals in recent = years, I have no idea which of them actually perform well across diverse ma= terials.
A study that compares not only energetics, but also comp= uted electron densities, across diverse materials (molecules, solids, trans= ition states, etc.) could be extremely valuable for figuring out which rece= ntly developed functionals actually perform well.

= One of the things the Science article claims is that the recent functionals= are getting worse on the electron densities, but as you have pointed out, = we don't necessarily know whether this is truly the case. Particularly,= because the Science article tested such a limited set of materials (i.e., = single closed shell atoms and atomic cations) for the densities but cited e= nergies for entirely different material types, and as you pointed out the f= unctionals tested omitted many recent approaches developed by diverse resea= rch groups.

It would be great if someone could do = a more rigorous and inclusive study.

Tom

On Thu, Jan 26, 2017 = at 2:56 PM, Susi Lehtola susi.lehtola * alumni.helsinki.fi <owner-chemistry=-=ccl.net> wr= ote:

Sent to CCL by: Susi Lehtola [susi.lehtola---alumni.helsink<= wbr>i.fi]
On 01/26/2017 10:16 AM, Thomas Manz thomasamanz_._gmail.com wrote:
A recent issue of Science contained an interesting article "Density functional theory is
straying from the path toward the exact functional"[1].

 This has already been discussed on the list in the thread
=C2=A0"DFT discovers it's recapitulating QSAR"

I'd like to repeat my arguments in
http://www.ccl.net/cgi-bin/ccl/messa= ge-new?2017+01+06+006

that you could rewrite the result of the study as a much less catching &quo= t;Minnesota functionals fail to reproduce electron density in small atoms a= nd cations"
--
-----------------------------------------------------------------= ------
Mr. Susi Lehtola, PhD=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Chemis= t Postdoctoral Fellow
susi.lehtola|-|alumni.helsinki.fi=C2=A0 =C2=A0Lawrence Berkeley Na= tional Laboratory
http://www.helsinki.fi/~jzlehtol=C2=A0 USA
-----------------------------------------------------------------= ------



-=3D This is automatically added to each message by the mailing script =3D-=
E-mail to subscribers: CHEMISTRY=-=ccl.net or use:
=C2=A0 =C2=A0 =C2=A0http://www.ccl.net/cgi-bin/ccl/send_ccl_message

E-mail to administrators: CHEMISTRY-REQUEST=-=ccl.net or use
=C2=A0 =C2=A0 =C2=A0http://www.ccl.net/cgi-bin/ccl/send_ccl_message

Subscribe/Unsubscribe:=C2=A0 =C2=A0 =C2=A0 http://www.cc= l.net/chemistry/sub_unsub.shtml

Before posting, check wait time at: http://www.ccl.net

Job: http://www.ccl.net/jobs Conferences: http://server.ccl.net/chemistry/announcements/conferences/

Search Messages: http://www.ccl.net/chemistry/searchccl/index.shtml
=C2=A0 =C2=A0 =C2=A0http://www.ccl.net/spammers.txt

RTFI: http://www.ccl.net/chemistry/aboutcc= l/instructions/



--001a113778c6768fee05470b411f--