From owner-chemistry@ccl.net Mon Apr 27 11:08:01 2020 From: "Tymofii Nikolaienko tim_mail(~)ukr.net" To: CCL Subject: CCL: which charge partitioning methods always give non-negative atom-in-material densities? Message-Id: <-54049-200427060540-3698-GsyM0a05gkrt1AbOzjm9Zw|a|server.ccl.net> X-Original-From: Tymofii Nikolaienko Content-Language: uk Content-Type: multipart/alternative; boundary="------------ECC00E976AFEC49FE9AD5D5B" Date: Mon, 27 Apr 2020 13:05:31 +0300 MIME-Version: 1.0 Sent to CCL by: Tymofii Nikolaienko [tim_mail##ukr.net] This is a multi-part message in MIME format. --------------ECC00E976AFEC49FE9AD5D5B Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Dear Tom, if you are interested in partitioning the spatial electron density distribution among the atoms or bonds, you might consider CLPO method (described in [ Int.J.Quantum Chem. (2019), 119, e25798, DOI: 10.1002/qua.25798 ]). It works with the density matrix in NAO basis, but is focused on the spatial distribution of the density/densities, not merely on the integrated quantity contributing to the charge. It  also, in a sense, implicitly addresses the question about partitioning those 'cross terms' which integrate to zero. Best regards, Tymofii 25.04.2020 19:27, Thomas Manz thomasamanz/agmail.com пише: > Hi Susi and Hannes, > > Thanks for your replies. > > (a) The Mulliken method assigns negative electron orbital populations > on some atoms in materials. This issue was already discussed with > examples in Mulliken's original 1955 paper (see Table V and text > discussion in J Chem Phys 23, 1955, 1833-1840, DOI: > 10.1063/1.1740588). Consequently, Mulliken's method assigns negative > electron density to some atoms at some positions in space. > > (b) Because the NPA localized orbitals are orthonormal, and their > assigned partial occupancies are non-negative, the overlap or cross > term between two localized orbitals integrates to zero (because the > localized orbitals are orthonormal) leaving a net non-negative > contribution to each atom's integrated population from each localized > orbital. > > However, my question concerns the electron density value assigned to > each atom for a particular spatial position. It is not a question > about net atomic charges (of course those can be positive, negative, > and zero) or about the integrated number of electrons assigned to an > atom (i.e., the populations). For example, if the electron density at > a particular spatial position is 17.1 electrons/bohr^3, do any of > these methods ever assign a negative electron density value (e.g., > -0.35 electrons/bohr^3) to any atom at any spatial position. In this > example, the electron density assigned to the other atoms would thus > sum to 17.45 electrons/bohr^3, to reproduce the electron density value > of 17.1 electrons/bohr^3 when summed over all atoms at this particular > spatial position. > > This question is an extremely hard one, because it involves the sum of > three terms: the self-term between localized orbital on atom A, the > self-term between localized orbital on atom B, and the corresponding > cross term. Only if the magnitude of the cross term can exceed the > self-terms at some location in space then the assigned electron > density distribution may be negative at some spatial position for some > atom. For the four methods mentioned in my email, I am having trouble > figuring out if or when this could occur. > > The NPA method does not appear to describe a particular protocol for > dividing the cross terms between two atoms. Since the NPA cross terms > integrate to zero (i.e., the NAO's are orthonormal), the NPA method > has not yet concerned itself with a particular protocol for dividing > the cross terms. Accordingly, the NPA method yields non-negative > integrated populations, but appears to have no specific electron > distributions assigned to particular atoms in the material. However, > one could easily do that by assuming a cross-term partitioning ala > Mulliken (in which each atom gets half the cross term) or Bickelhaupt > (in which each cross-term is divided proportionally to the > corresponding self-terms) except using the orthonormal NAOs as the > basis functions. This would, of course, return the NPA integrated > populations, but also assign an electron density distribution to each > atom in the material. > > (c) The Bickelhaupt method I referred to was intended to mean their > modified Mulliken-like scheme (eqn 11 of their paper). Mulliken's > method assigns half of each localized orbitals cross term each of the > two atoms. In the Bickelhaupt scheme, the cross term for localized > orbital i on atom A and localized orbital j on atom B is divided as > follows: > > fraction of i-j cross-term assigned to atom A = proportional to > qii/(qii + qjj), where qii is the self-population of orbital i on atom A > fraction of i-j cross-term assigned to atom B = proportional to > qjj/(qii + qjj), where qjj is the self-population of orbital j on atom B > (These sum to one.) > > (d) I understand the point about MP2 population analysis yielding > potentially negative populations, in cases where it yields negative > eigenvalues for one of the natural orbitals (eigenstates of MP2 > density matrix). This, of course, is an important point. So, let me > rephrase or restrict my original question to those cases where the > quantum chemistry density is N-representable (i.e., eigenvalues of the > natural spin-orbitals are between 0 and 1 inclusive). > > (e) I do not yet fully understand the nature of the projections > involved in the IBO method. Consequently, it is hard for me to > completely follow your argument about why the IBO method is expected > to always yield non-negative integrated populations. I do understand > that if the projection operator has all non-negative eigenvalues then > its double contraction with any vector will yield a non-negative > population. (This is a basic property of all positive semi-definite > matrices.) So, I understand the gist of your argument, even if some of > the finer details of the IBO projection are still unclear to me. > Nevertheless, I am particularly interested in whether the IBO method > may assign a negative electron density value (at a particular spatial > position) to any atom. > > Sincerely, > > Tom > > > On Sat, Apr 25, 2020 at 3:08 AM Susi Lehtola > susi.lehtola/aalumni.helsinki.fi > > wrote: > > > Sent to CCL by: Susi Lehtola [susi.lehtola*o*alumni.helsinki.fi > ] > On 4/25/20 8:08 AM, Thomas Manz thomasamanz|-|gmail.com > wrote: > > Dear Colleagues, > > > > While writing a journal manuscript, I encountered the following > technical > > question, to which I do not currently know the answer. > > > > Is it known which of the following charge partitioning methods > (if any) can > > sometimes assign a negative electron density value to one (or > more) atoms at > > some position(s) in space? > > > > (1) Intrinsic bond orbital (IBO) method by Knizia (J Chem Theory > Comput, 2013, > > 9, 4834−4843, DOI: 10.1021/ct400687b) > > > > (2) Bickelhaupt method by Bickelhaupt et al. (Organometallics > 1996, 15, > > 2923-2931, DOI: 10.1021/om950966x) > > > > (3) Minimal basis set Bickelhaupt (MBSBickelhaupt) method by Cho > et al. > > (ChemPhysChem, 2020, 21, 688-696, DOI:10.1002/cphc.202000040) > > > > (4) Natural population analysis (NPA) by Reed, Weinstock, and > Weinhold (J Chem > > Phys, 1985, 83, 735-746, DOI: 10.1063/1.449486) > > > > If you have insights into this question, would you be able to > provide a specific > > example, reference, or brief mathematical explanation? > > Dear Tom, > > > this truly is a technical question. Namely, since the electron > density is > positive semidefinite, n(r) >= 0 everywhere, a charge partitioning > method that > assigned a *negative electronic charge* to one or more atoms would > necessarily > mean grave mathematical problems: any well-based method should > yield at least > zero electrons for any atom. > > (1) IBO belongs to the class of generalized Pipek-Mezey methods > (10.1021/ct401016x) that produce localized orbitals from a given > definition of > atomic partial charges. The partial charges in IBO are from the > intrinsic atomic > orbitals (IAO) from the same paper. The IAOs are just taken as the > occupied > atomic orbitals for the atomic ground state. > > Since IAO assigns partial charges by projection (like most of the > other usable > generalized Pipek-Mezey methods that are mathematically > well-defined, unlike the > original Pipek-Mezey scheme), it is not possible to get negative > electron > densities with IAO. > > Projection operators can only have eigenvalues between 0 and 1; 0 > for components > that cannot be at all described in the other basis and 1 for > components that can > be exactly represented in the other basis. > > (2) It is not clear which method you mean; the Bickelhaupt et al > paper uses two > > from the literature and describes two methods. The first one > defines partial > charges by integrating the difference of the molecular electron > density and the > superposition of atomic densities over the Voronoi cell, and the > second is a > modification to the Mulliken scheme where off-diagonal elements > are also > included; like the Mulliken scheme, this one is also > mathematically ill-defined > since it does not have a basis set limit (10.1021/ct401016x). > > I have a vague recollection of seeing something similar to the  > modified > Mulliken scheme Bickelhaupt used in much earlier literature. It is > not obvious > how electron density would be assigned by the Voronoi scheme, > since it does not > use the nuclear charge at all. > > (3) This is Bickelhaupt's scheme; one just projects into a minimal > basis before > performing the Mulliken-style analysis. > > (4) As far as I know, NPA is also based on projections, and > thereby should not > have problems with negative densities. > > Even though the Mulliken scheme is not mathematically > well-founded, I don't > think it is possible to get negative electron densities with it: > if you span the > molecular basis with basis functions on a single atom, all > electrons will be > counted on that center, and the others will have zero electrons each. > -- > ------------------------------------------------------------------ > Mr. Susi Lehtola, PhD             Junior Fellow, Adjunct Professor > susi.lehtola##alumni.helsinki.fi >  University of Helsinki > http://susilehtola.github.io/    Finland > ------------------------------------------------------------------ > Susi Lehtola, dosentti, FT        tutkijatohtori > susi.lehtola##alumni.helsinki.fi >  Helsingin yliopisto > http://susilehtola.github.io/ > ------------------------------------------------------------------ > > > > -= This is automatically added to each message by the mailing > script =- > E-mail to subscribers: CHEMISTRY]_[ccl.net > or use:> > E-mail to administrators: CHEMISTRY-REQUEST]_[ccl.net > or use> Conferences: > http://server.ccl.net/chemistry/announcements/conferences/> > --------------ECC00E976AFEC49FE9AD5D5B Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit

Dear Tom,

if you are interested in partitioning the spatial electron density distribution among the atoms or bonds,
you might consider CLPO method (described in [ Int.J.Quantum Chem. (2019), 119, e25798, DOI: 10.1002/qua.25798 ]).
It works with the density matrix in NAO basis, but is focused on the spatial distribution of the density/densities, not merely
on the integrated quantity contributing to the charge. It  also, in a sense, implicitly addresses the question about partitioning
those 'cross terms' which integrate to zero.


Best regards,
Tymofii


25.04.2020 19:27, Thomas Manz thomasamanz/agmail.com пише:
Hi Susi and Hannes,

Thanks for your replies. 

(a) The Mulliken method assigns negative electron orbital populations on some atoms in materials. This issue was already discussed with examples in Mulliken's original 1955 paper (see Table V and text discussion in J Chem Phys 23, 1955, 1833-1840, DOI: 10.1063/1.1740588). Consequently, Mulliken's method assigns negative electron density to some atoms at some positions in space.

(b) Because the NPA localized orbitals are orthonormal, and their assigned partial occupancies are non-negative, the overlap or cross term between two localized orbitals integrates to zero (because the localized orbitals are orthonormal) leaving a net non-negative contribution to each atom's integrated population from each localized orbital. 

However, my question concerns the electron density value assigned to each atom for a particular spatial position. It is not a question about net atomic charges (of course those can be positive, negative, and zero) or about the integrated number of electrons assigned to an atom (i.e., the populations). For example, if the electron density at a particular spatial position is 17.1 electrons/bohr^3, do any of these methods ever assign a negative electron density value (e.g., -0.35 electrons/bohr^3) to any atom at any spatial position. In this example, the electron density assigned to the other atoms would thus sum to 17.45 electrons/bohr^3, to reproduce the electron density value of 17.1 electrons/bohr^3 when summed over all atoms at this particular spatial position.

This question is an extremely hard one, because it involves the sum of three terms: the self-term between localized orbital on atom A, the self-term between localized orbital on atom B, and the corresponding cross term. Only if the magnitude of the cross term can exceed the self-terms at some location in space then the assigned electron density distribution may be negative at some spatial position for some atom. For the four methods mentioned in my email, I am having trouble figuring out if or when this could occur.

The NPA method does not appear to describe a particular protocol for dividing the cross terms between two atoms. Since the NPA cross terms integrate to zero (i.e., the NAO's are orthonormal), the NPA method has not yet concerned itself with a particular protocol for dividing the cross terms. Accordingly, the NPA method yields non-negative integrated populations, but appears to have no specific electron distributions assigned to particular atoms in the material. However, one could easily do that by assuming a cross-term partitioning ala Mulliken (in which each atom gets half the cross term) or Bickelhaupt (in which each cross-term is divided proportionally to the corresponding self-terms) except using the orthonormal NAOs as the basis functions. This would, of course, return the NPA integrated populations, but also assign an electron density distribution to each atom in the material.

(c) The Bickelhaupt method I referred to was intended to mean their modified Mulliken-like scheme (eqn 11 of their paper). Mulliken's method assigns half of each localized orbitals cross term each of the two atoms. In the Bickelhaupt scheme, the cross term for localized orbital i on atom A and localized orbital j on atom B is divided as follows:

fraction of i-j cross-term assigned to atom A = proportional to qii/(qii + qjj), where qii is the self-population of orbital i on atom A
fraction of i-j cross-term assigned to atom B =  proportional to qjj/(qii + qjj), where qjj is the self-population of orbital j on atom B
(These sum to one.)

(d) I understand the point about MP2 population analysis yielding potentially negative populations, in cases where it yields negative eigenvalues for one of the natural orbitals (eigenstates of MP2 density matrix). This, of course, is an important point. So, let me rephrase or restrict my original question to those cases where the quantum chemistry density is N-representable (i.e., eigenvalues of the natural spin-orbitals are between 0 and 1 inclusive).

(e) I do not yet fully understand the nature of the projections involved in the IBO method. Consequently, it is hard for me to completely follow your argument about why the IBO method is expected to always yield non-negative integrated populations. I do understand that if the projection operator has all non-negative eigenvalues then its double contraction with any vector will yield a non-negative population. (This is a basic property of all positive semi-definite matrices.) So, I understand the gist of your argument, even if some of the finer details of the IBO projection are still unclear to me. Nevertheless, I am particularly interested in whether the IBO method may assign a negative electron density value (at a particular spatial position) to any atom.

Sincerely,

Tom


On Sat, Apr 25, 2020 at 3:08 AM Susi Lehtola susi.lehtola/aalumni.helsinki.fi <owner-chemistry]_[ccl.net> wrote:

Sent to CCL by: Susi Lehtola [susi.lehtola*o*alumni.helsinki.fi]
On 4/25/20 8:08 AM, Thomas Manz thomasamanz|-|gmail.com wrote:
> Dear Colleagues,
>
> While writing a journal manuscript, I encountered the following technical
> question, to which I do not currently know the answer.
>
> Is it known which of the following charge partitioning methods (if any) can
> sometimes assign a negative electron density value to one (or more) atoms at
> some position(s) in space?
>
> (1) Intrinsic bond orbital (IBO) method by Knizia (J Chem Theory Comput, 2013,
> 9, 4834−4843, DOI: 10.1021/ct400687b)
>
> (2) Bickelhaupt method by Bickelhaupt et al. (Organometallics 1996, 15,
> 2923-2931, DOI: 10.1021/om950966x)
>
> (3) Minimal basis set Bickelhaupt (MBSBickelhaupt) method by Cho et al.
> (ChemPhysChem, 2020, 21, 688-696, DOI:10.1002/cphc.202000040)
>
> (4) Natural population analysis (NPA) by Reed, Weinstock, and Weinhold (J Chem
> Phys, 1985, 83, 735-746, DOI: 10.1063/1.449486)
>
> If you have insights into this question, would you be able to provide a specific
> example, reference, or brief mathematical explanation?

Dear Tom,


this truly is a technical question. Namely, since the electron density is
positive semidefinite, n(r) >= 0 everywhere, a charge partitioning method that
assigned a *negative electronic charge* to one or more atoms would necessarily
mean grave mathematical problems: any well-based method should yield at least
zero electrons for any atom.

(1) IBO belongs to the class of generalized Pipek-Mezey methods
(10.1021/ct401016x) that produce localized orbitals from a given definition of
atomic partial charges. The partial charges in IBO are from the intrinsic atomic
orbitals (IAO) from the same paper. The IAOs are just taken as the occupied
atomic orbitals for the atomic ground state.

Since IAO assigns partial charges by projection (like most of the other usable
generalized Pipek-Mezey methods that are mathematically well-defined, unlike the
original Pipek-Mezey scheme), it is not possible to get negative electron
densities with IAO.

Projection operators can only have eigenvalues between 0 and 1; 0 for components
that cannot be at all described in the other basis and 1 for components that can
be exactly represented in the other basis.

(2) It is not clear which method you mean; the Bickelhaupt et al paper uses two
> from the literature and describes two methods. The first one defines partial
charges by integrating the difference of the molecular electron density and the
superposition of atomic densities over the Voronoi cell, and the second is a
modification to the Mulliken scheme where off-diagonal elements are also
included; like the Mulliken scheme, this one is also mathematically ill-defined
since it does not have a basis set limit (10.1021/ct401016x).

I have a vague recollection of seeing something similar to the  modified
Mulliken scheme Bickelhaupt used in much earlier literature. It is not obvious
how electron density would be assigned by the Voronoi scheme, since it does not
use the nuclear charge at all.

(3) This is Bickelhaupt's scheme; one just projects into a minimal basis before
performing the Mulliken-style analysis.

(4) As far as I know, NPA is also based on projections, and thereby should not
have problems with negative densities.

Even though the Mulliken scheme is not mathematically well-founded, I don't
think it is possible to get negative electron densities with it: if you span the
molecular basis with basis functions on a single atom, all electrons will be
counted on that center, and the others will have zero electrons each.
--
------------------------------------------------------------------
Mr. Susi Lehtola, PhD             Junior Fellow, Adjunct Professor
susi.lehtola##alumni.helsinki.fi   University of Helsinki
http://susilehtola.github.io/     Finland
------------------------------------------------------------------
Susi Lehtola, dosentti, FT        tutkijatohtori
susi.lehtola##alumni.helsinki.fi   Helsingin yliopisto
http://susilehtola.github.io/
------------------------------------------------------------------



E-mail to subscribers: CHEMISTRY]_[ccl.net or use:
      http://www.ccl.net/cgi-bin/ccl/send_ccl_message

E-mail to administrators: CHEMISTRY-REQUEST]_[ccl.net or use
      http://www.ccl.net/cgi-bin/ccl/send_ccl_message
      http://www.ccl.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
      http://www.ccl.net/spammers.txt

RTFI: http://www.ccl.net/chemistry/aboutccl/instructions/


--------------ECC00E976AFEC49FE9AD5D5B-- From owner-chemistry@ccl.net Mon Apr 27 11:43:01 2020 From: "Marc M MEUNIER marc.meunier^3ds.com" To: CCL Subject: CCL: Molecular Simulation Special Issue: Materials Studio 20th Anniversary Message-Id: <-54050-200427105236-17205-jXWX68X0CPz1rTdhhIOIgg(-)server.ccl.net> X-Original-From: "Marc M MEUNIER" Date: Mon, 27 Apr 2020 10:52:35 -0400 Sent to CCL by: "Marc M MEUNIER" [marc.meunier|,|3ds.com] Call for Paper! - Extended Deadline - July 2020 In 2020 Materials Studio will celebrate its 20th anniversary! Over 25,000 peer-reviewed scientific papers were published using one or more of its compute solvers such as CASTEP, DMol3 or GULP It is our pleasure to invite you to submit your contribution - a research paper, a letter or a review, to the Molecular Simulation special issue of Materials Studio 2020. [1] In 2008, a similar special issue of Molecular Simulation [2] had over 50 papers published. We sincerely hope that the 2020 edition will be as rich and popular! See the journal' Call for Papers https://think.taylorandfrancis.com/molecular-simulation-materials-studio-20th-anniversary Regards Marc Meunier, Molecular Simulation Editorial Board marc.meunier-at-3ds.com [1] https://www.tandfonline.com/loi/gmos20 [2] Molecular Simulation, Vol. 34, Nos. 1015, SeptemberDecember 2008 From owner-chemistry@ccl.net Mon Apr 27 12:23:00 2020 From: "Partha Sengupta anapspsmo++gmail.com" To: CCL Subject: CCL: TDDFT for UV-visible spectra Message-Id: <-54051-200426143441-13614-m0zlEuFpBkvDHi426m//yA/a\server.ccl.net> X-Original-From: Partha Sengupta Content-Type: multipart/alternative; boundary="0000000000009c42fb05a435d991" Date: Mon, 27 Apr 2020 00:04:24 +0530 MIME-Version: 1.0 Sent to CCL by: Partha Sengupta [anapspsmo*_*gmail.com] --0000000000009c42fb05a435d991 Content-Type: text/plain; charset="UTF-8" Thank you for your reply. Partha On Sun, Apr 26, 2020 at 11:21 PM Pierre Archirel pierre.archirel|-| universite-paris-saclay.fr wrote: > > Sent to CCL by: "Pierre Archirel" [pierre.archirel(0) > universite-paris-saclay.fr] > This is an answer to Partha Sarathi Sengupta, > > Dear colleague, > Your short question raises three main difficulties: > 1- the TDDFT line at the equilibrium geometry generally does not coincide > with the maximum of the absorption band. > 2- I guess you are using DFT, which is fast and often efficient, but many > functionals are available, choosing the best one requires many tests. > 3- if your system is in solution you must model the solvent > > Since you mention Cu and Ni complexes, I may advertize my work on the > Ag(CN)2^2- system in water, where I simulated with success absorption > spectra with the TDDFT method, the B3LYP functional and the SMD solvent: > > P. Archirel et al. PCCP, 2017, 19 23068 > > But note that B3LYP often yield poor results, in this case I recommend the > 'long range corrected' functional lc-wPBE where the w parameter can be > optimised, so as to reproduce high level quantum results on little model > systems. Allow me again to advertise my work on absorption spectra of > peptides: > > P. Archirel et al. J. Phys. Chem. B 2019, 123, 90879097 > > In any case fast choices and calculations can yield poor results! > Best wishes, > Pierre Archirel > ICP Universite Paris-Saclay, Orsay, France > pierre.archirel&universite-paris-saclay.fr> > > -- *Dr. Partha Sarathi SenguptaAssociate ProfessorVivekananda Mahavidyalaya, Burdwan* --0000000000009c42fb05a435d991 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Thank you for your reply.
Partha

On Sun, Apr 26, = 2020 at 11:21 PM Pierre Archirel pierre.archirel|-|universite-paris-saclay.fr <owner-chemistry++ccl.net> wrote:

Sent to CCL by: "Pierre=C2=A0 Archirel" [pierre.archirel(0)universite-paris-saclay.fr]
This is an answer to Partha Sarathi Sengupta,

Dear colleague,
Your short question raises three main difficulties:
1- the TDDFT line at the equilibrium geometry generally does not coincide w= ith the maximum of the absorption band.
2- I guess you are using DFT, which is fast and often efficient, but many f= unctionals are available, choosing the best one requires many tests.
3- if your system is in solution you must model the solvent

Since you mention Cu and Ni complexes, I may advertize my work on the Ag(CN= )2^2- system in water, where I simulated with success absorption spectra wi= th the TDDFT method, the B3LYP functional and the SMD solvent:

P. Archirel et al. PCCP, 2017, 19 23068

But note that B3LYP often yield poor results, in this case I recommend the = 'long range corrected' functional lc-wPBE where the w parameter can= be optimised, so as to reproduce high level quantum results on little mode= l systems. Allow me again to advertise my work on absorption spectra of pep= tides:

P. Archirel et al. J. Phys. Chem. B 2019, 123, 90879097

In any case fast choices and calculations can yield poor results!
Best wishes,
Pierre Archirel
ICP Universite Paris-Saclay, Orsay, France
pierre.archirel&universite-paris-saclay.fr



-=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=A0 http://www.ccl.net/cgi-bin/ccl/s= end_ccl_message

E-mail to administrators: CHEMISTRY-REQUEST++ccl.net or use
=C2=A0 =C2=A0 =C2=A0 http://www.ccl.net/cgi-bin/ccl/s= end_ccl_message
=C2=A0 =C2=A0 =C2=A0 http://www.ccl.net/chemistry/sub_un= sub.shtml

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

Job: http://www.ccl.net/jobs
Conferences: http://server.ccl.net/chemist= ry/announcements/conferences/

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

RTFI: http://www.ccl.net/chemistry/aboutccl/ins= tructions/




--
Dr. Partha Sarat= hi Sengupta
Associate Professor
Vivekananda Mahavidyalaya, Burdwan
--0000000000009c42fb05a435d991-- From owner-chemistry@ccl.net Mon Apr 27 15:15:00 2020 From: "Wojciech Kolodziejczyk dziecial|a|icnanotox.org" To: CCL Subject: CCL: TDDFT for UV-visible spectra Message-Id: <-54052-200427145216-3859-hTTG7xVmjwppYAr5VKPWfQ%%server.ccl.net> X-Original-From: Wojciech Kolodziejczyk Content-Type: multipart/alternative; boundary="00000000000054fc4205a44a36ca" Date: Mon, 27 Apr 2020 13:51:34 -0500 MIME-Version: 1.0 Sent to CCL by: Wojciech Kolodziejczyk [dziecial() icnanotox.org] --00000000000054fc4205a44a36ca Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi, You need to remember that when you work with long range functional as functional lc-wPBE there is a lot of extra work. Text me in private and I can provide you with step by step solution if you meet any problem. W. pon., 27 kwi 2020 o 13:12 Partha Sengupta anapspsmo++gmail.com < owner-chemistry-.-ccl.net> napisa=C5=82(a): > Thank you for your reply. > Partha > > On Sun, Apr 26, 2020 at 11:21 PM Pierre Archirel pierre.archirel|-| > universite-paris-saclay.fr wrote: > >> >> Sent to CCL by: "Pierre Archirel" [pierre.archirel(0) >> universite-paris-saclay.fr] >> This is an answer to Partha Sarathi Sengupta, >> >> Dear colleague, >> Your short question raises three main difficulties: >> 1- the TDDFT line at the equilibrium geometry generally does not coincid= e >> with the maximum of the absorption band. >> 2- I guess you are using DFT, which is fast and often efficient, but man= y >> functionals are available, choosing the best one requires many tests. >> 3- if your system is in solution you must model the solvent >> >> Since you mention Cu and Ni complexes, I may advertize my work on the >> Ag(CN)2^2- system in water, where I simulated with success absorption >> spectra with the TDDFT method, the B3LYP functional and the SMD solvent: >> >> P. Archirel et al. PCCP, 2017, 19 23068 >> >> But note that B3LYP often yield poor results, in this case I recommend >> the 'long range corrected' functional lc-wPBE where the w parameter can = be >> optimised, so as to reproduce high level quantum results on little model >> systems. Allow me again to advertise my work on absorption spectra of >> peptides: >> >> P. Archirel et al. J. Phys. Chem. B 2019, 123, 90879097 >> >> In any case fast choices and calculations can yield poor results! >> Best wishes, >> Pierre Archirel >> ICP Universite Paris-Saclay, Orsay, France >> pierre.archirel&universite-paris-saclay.fr >> >> >> >> -=3D This is automatically added to each message by the mailing script = =3D- >> E-mail to subscribers: CHEMISTRY{:}ccl.net or use:>> >> E-mail to administrators: CHEMISTRY-REQUEST{:}ccl.net or use>> >> >> > > -- > > > *Dr. Partha Sarathi SenguptaAssociate ProfessorVivekananda Mahavidyalaya, > Burdwan* > --00000000000054fc4205a44a36ca Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi,
You need to remember that when you work with long = range functional as functional lc-wPBE there is a lot of extra work. Text m= e in private and I can provide you with step by step solution if you meet a= ny problem.

W.

pon., 27 kwi 2020 o 13:12=C2= =A0Partha Sengupta anapspsmo++gmail.com &l= t;owner-chemistry-.-ccl.net>= ; napisa=C5=82(a):
Thank you for your reply.
Partha

On Sun, Apr 2= 6, 2020 at 11:21 PM Pierre Archirel pierre.archirel|-|universite-paris-saclay.fr &= lt;owner= -chemistry{:}ccl.net> wrote:

Sent to CCL by: "Pierre=C2=A0 Archirel" [pierre.archirel(0)universite-paris-saclay.fr]
This is an answer to Partha Sarathi Sengupta,

Dear colleague,
Your short question raises three main difficulties:
1- the TDDFT line at the equilibrium geometry generally does not coincide w= ith the maximum of the absorption band.
2- I guess you are using DFT, which is fast and often efficient, but many f= unctionals are available, choosing the best one requires many tests.
3- if your system is in solution you must model the solvent

Since you mention Cu and Ni complexes, I may advertize my work on the Ag(CN= )2^2- system in water, where I simulated with success absorption spectra wi= th the TDDFT method, the B3LYP functional and the SMD solvent:

P. Archirel et al. PCCP, 2017, 19 23068

But note that B3LYP often yield poor results, in this case I recommend the = 'long range corrected' functional lc-wPBE where the w parameter can= be optimised, so as to reproduce high level quantum results on little mode= l systems. Allow me again to advertise my work on absorption spectra of pep= tides:

P. Archirel et al. J. Phys. Chem. B 2019, 123, 90879097

In any case fast choices and calculations can yield poor results!
Best wishes,
Pierre Archirel
ICP Universite Paris-Saclay, Orsay, France
pierre.archirel&universite-paris-saclay.fr



-=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=A0 http://www.ccl.net/cgi-bin/ccl/s= end_ccl_message

E-mail to administrators: CHEMISTRY-REQUEST{:}ccl.net or use
=C2=A0 =C2=A0 =C2=A0 http://www.ccl.net/cgi-bin/ccl/s= end_ccl_message
=C2=A0 =C2=A0 =C2=A0 http://www.ccl.net/chemistry/sub_un= sub.shtml

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

Job: http://www.ccl.net/jobs
Conferences: http://server.ccl.net/chemist= ry/announcements/conferences/

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

RTFI: http://www.ccl.net/chemistry/aboutccl/ins= tructions/




--
Dr. Partha Sarathi Sengupta
Associate P= rofessor
Vivekananda Mahavidyalaya, Burdwan
--00000000000054fc4205a44a36ca--