From owner-chemistry@ccl.net Wed Jul 1 06:55:01 2020 From: "Brian Salter-Duke brian.james.duke(!)gmail.com" To: CCL Subject: CCL: VB2000 Message-Id: <-54127-200701062048-9311-76FYkF3zUhGBDyEgFDRH2w]=[server.ccl.net> X-Original-From: Brian Salter-Duke Content-Type: multipart/alternative; boundary="000000000000dad62b05a95ea4b7" Date: Wed, 1 Jul 2020 20:20:30 +1000 MIME-Version: 1.0 Sent to CCL by: Brian Salter-Duke [brian.james.duke(a)gmail.com] --000000000000dad62b05a95ea4b7 Content-Type: text/plain; charset="UTF-8" I am very pleased to announce that the VB2000 program now has two additional authors, Rodrigo da Silva Bitzer and David de Sousa, both from Brazil. Since the original author, Jiabo Li, has moved out of quantum chemistry and I am now over 80 years old, it is great to have new younger scientists working on this program. While I am here, if anyone has any ideas to expand the VB2000 program with new code, please let me know. -- Brian Salter-Duke (aka Brian Duke) Brian.James.Duke() gmail.com --000000000000dad62b05a95ea4b7 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

I am very pleased to announce that = the VB2000 program now has
two additional authors, Rodrigo da Silva Bitz= er and David de Sousa,
both from Brazil. Since the original author, Jiab= o Li, has moved out
of quantum chemistry and I am now over 80 years old,= it is great to
have new younger scientists working on this program.
=
While I am here, if anyone has any ideas to expand the VB2000 programwith new code, please let me know.

--
Brian Salter-Du= ke (aka Brian Duke)
Brian.James.Duke() gmail.com
--000000000000dad62b05a95ea4b7-- From owner-chemistry@ccl.net Wed Jul 1 07:29:00 2020 From: "Brian Salter-Duke brian.james.duke++gmail.com" To: CCL Subject: CCL: VB2000 Message-Id: <-54128-200701065303-11144-dMdfNmI/oQl/rLPGlQw1eg . server.ccl.net> X-Original-From: Brian Salter-Duke Content-Type: multipart/alternative; boundary="00000000000037762f05a95f18de" Date: Wed, 1 Jul 2020 20:52:45 +1000 MIME-Version: 1.0 Sent to CCL by: Brian Salter-Duke [brian.james.duke**gmail.com] --00000000000037762f05a95f18de Content-Type: text/plain; charset="UTF-8" I am very pleased to announce that the VB2000 program now has two additional authors, Rodrigo da Silva Bitzer and David de Sousa, both from Brazil. Since the original author, Jiabo Li, has moved out of quantum chemistry and I am now over 80 years old, it is great to have new younger scientists working on this program. While I am here, if anyone has any ideas to expand the VB2000 program with new code, please let me know. Brian Duke. -- Brian Salter-Duke (aka Brian Duke) Brian.James.Duke,+,gmail.com --00000000000037762f05a95f18de Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I am very pleased to announce that the VB2000 program now = has
two additional authors, Rodrigo da Silva Bitzer and David de Sousa,<= br>both from Brazil. Since the original author, Jiabo Li, has moved out
= of quantum chemistry and I am now over 80 years old, it is great to
have= new younger scientists working on this program.

While I am here, if= anyone has any ideas to expand the VB2000 program
with new code, please= let me know.

Brian Duke.

--
= Brian Salter-Duke (aka Brian Duke)
Brian.James.Duke,+,gmail.com
--00000000000037762f05a95f18de-- From owner-chemistry@ccl.net Wed Jul 1 09:20:00 2020 From: "Caio Firme firme.caio-.-gmail.com" To: CCL Subject: CCL: VB2000 Message-Id: <-54129-200701091831-27637-3Nj2zZwvCfCCfgRczsR8PQ#,#server.ccl.net> X-Original-From: Caio Firme Content-Type: multipart/alternative; boundary="0000000000007eae9d05a96120bb" Date: Wed, 1 Jul 2020 10:18:14 -0300 MIME-Version: 1.0 Sent to CCL by: Caio Firme [firme.caio_-_gmail.com] --0000000000007eae9d05a96120bb Content-Type: text/plain; charset="UTF-8" Hello Brian. What a great news! I hope you will return to host the stand-alone version in VB2000's own site. I also hope you might expand the number of electron of the VB group. I am a great enthusiastic of modern VB theory. I believe that VB2000 gives a important contribution to the Chemistry as a science and discipline because it is very important to have wave function alternative to molecular orbital theory. I myself gave a tiny contribution using VB2000 in a couple of papers and in my book (Introductory Organic Chemistry and Hydrocarbons - A physical chemistry approach). I wish the new VB2000 team a successful journey. All the best Caio Em qua, 1 de jul de 2020 09:42, Brian Salter-Duke brian.james.duke(!) gmail.com escreveu: > > I am very pleased to announce that the VB2000 program now has > two additional authors, Rodrigo da Silva Bitzer and David de Sousa, > both from Brazil. Since the original author, Jiabo Li, has moved out > of quantum chemistry and I am now over 80 years old, it is great to > have new younger scientists working on this program. > > While I am here, if anyone has any ideas to expand the VB2000 program > with new code, please let me know. > > -- > Brian Salter-Duke (aka Brian Duke) > Brian.James.Duke:gmail.com > --0000000000007eae9d05a96120bb Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hello Brian.

What a great news! I hope you will return to host the stand-alone version = in VB2000's own site. I also hope you might expand the number of electr= on of the VB group.=C2=A0

I am a great enthusiastic of modern VB theory. I believe that VB2000 give= s a important contribution to the Chemistry as a science and discipline bec= ause it is very important to have wave function alternative to molecular or= bital theory. I myself gave a tiny contribution using VB2000 in a couple of= papers and in my book (Introductory Organic Chemistry and Hydrocarbons - A= physical chemistry approach).

I wish the new VB2000 team a successful journey.

All the best

Caio

Em qua, 1 de jul de 2020 09:42, Brian Salter= -Duke brian.james.duke(!)gmail.com <owner-chemistry]|[ccl.net> esc= reveu:

I am very pleased to announce that the VB2000 program now has=
two additional authors, Rodrigo da Silva Bitzer and David de Sousa,
= both from Brazil. Since the original author, Jiabo Li, has moved out
of = quantum chemistry and I am now over 80 years old, it is great to
have ne= w younger scientists working on this program.

While I am here, if an= yone has any ideas to expand the VB2000 program
with new code, please le= t me know.

--
Brian Salter-Duke (aka Brian Duke)
Brian.James.Duke:gmai= l.com
--0000000000007eae9d05a96120bb-- From owner-chemistry@ccl.net Wed Jul 1 11:49:01 2020 From: "Sourabh Kumar sourabhkumar10021997 _ gmail.com" To: CCL Subject: CCL:G: Absorption spectrum of Tin atom involved molecule Message-Id: <-54130-200701112455-5975-q0DGXfFJR59UBiPgADu6Fw#,#server.ccl.net> X-Original-From: "Sourabh Kumar" Date: Wed, 1 Jul 2020 11:24:54 -0400 Sent to CCL by: "Sourabh Kumar" [sourabhkumar10021997 .. gmail.com] Hi everyone, I am trying to do absorption spectrum calculations of a Tin atom involved molecule(containing S, C, O and hydrogen atoms too) with the level of a theory of PBE/LANL2DZ ECP Gen. But the spectra it is producing is of very less oscillator strength. I have also tried many other methods like B3LYP, B97, BLYP, BHHLYP, wB97, wB97M with user- defined basis sets from basissetexchange.com but still, the oscillator strength is very week. I have used Qchem, orca and also Gaussian but from all, I am getting very weak oscillator strength. Could anyone please suggest what should I do here to solve this problem. Sourabh Kumar sourabhkumar10021997]_[gmail.com University of Bremen From owner-chemistry@ccl.net Wed Jul 1 16:22:00 2020 From: "Cody Aldaz craldaz**umich.edu" To: CCL Subject: CCL: Charge Message-Id: <-54131-200701145140-26173-L3MT4BASE3yHumMMyj18rQ%server.ccl.net> X-Original-From: Cody Aldaz Content-Type: multipart/alternative; boundary="000000000000df88b905a965c7cc" Date: Wed, 1 Jul 2020 14:51:22 -0400 MIME-Version: 1.0 Sent to CCL by: Cody Aldaz [craldaz*_*umich.edu] --000000000000df88b905a965c7cc Content-Type: text/plain; charset="UTF-8" Dear CCL users, I find it interesting that a similar discussion on this topic has sparked almost simultaneously on Matter Modeling Stack Exchange https://mattermodeling.stackexchange.com/q/1439/52 Of course this discussion of charge has been ongoing for many years and also across many different forums. But if you are inclined I encourage you to look at the current answers there and post an answer if you want to add more to the discussion, because this is a very important question. Best, Cody Aldaz On Mon, Jun 29, 2020 at 1:44 PM Thomas Manz thomasamanz%gmail.com < owner-chemistry:_:ccl.net> wrote: > Hi Stefan, > > I wanted to further clarify one aspect of my earlier response. > > Suppose that one has a NaCl crystal, for example. Using a Mulliken > population analysis, depending on the basis set, the populations of the Na > and Cl atoms could take on any values that sum to 11 + 17 = 28 electrons. > For example, one could have 11.3488 electrons on the Na atom and 28 - > 11.3488 = 16.6512 electrons on the Cl atom. Using a different basis set, > the Mulliken population analysis might yield 10.2342 electrons on the Na > atom and 28 - 10.2342 = 17.7658 electrons on the Cl atom. Using another > basis set, you might get 11.0000 electrons on the Na atom and 28 - 11.0000 > = 17.0000 electrons on the Cl atom. For any chosen basis set, the Mulliken > populations (or any other kind of populations) and their corresponding > atomic multipoles and charge penetration (i.e., Coulombic electrostatic > interaction between overlapping functions) integrals could be used as a > representation to expand the Coulomb operator (i.e., to calculate the > Coulomb interaction between electrons in the quantum chemistry > calculation). If the expansion is carried out to high enough order, then > its precision could be arbitrarily high (e.g., reproduce the Coulomb > interaction to machine precision). It is very clear to see this has nothing > to do with chemically meaningful atom-in-material descriptors, because in > case 1 the Na atom in the NaCl crystal would be assigned [sic] as an anion > and the Cl atom as a cation; in case 2 the Na atom in the NaCl crystal > would be assigned [sic] as an cation and the Cl atom as a anion; and in > case 3 the Na atom in the NaCl crystal would be assigned [sic] as neutral > (i.e., bearing no net charge) and the Cl atom also as neutral. Hence, the > Mulliken populations cannot be net atomic charges in general. > > Sincerely, > > Tom > > On Mon, Jun 29, 2020 at 9:27 AM Thomas Manz > wrote: > >> Hi Stefan, >> >> I think the confusion arises, because the Mulliken populations are >> sometimes confused with net atomic charges. >> >> The expansion of the electron density can be performed using any desired >> basis. In your application, the Mulliken partitioning is just a basis >> representation for expanding the electron density in terms of a distributed >> multipole expansion (e.g., up to quadrupole order). Yes, the Mulliken >> partitioning can be a mechanism to formulate a distributed multipole >> expansion of the electron density which can be a useful computational >> algorithm for computing electrostatic interactions during a quantum >> chemistry calculation. This is somewhat related to the fast multipole >> moments expansion of the Coulomb operator in quantum chemistry >> calculations. But, this is an entirely different topic than extracting >> chemically meaningful atom-in-material descriptors from a quantum chemistry >> calculation. >> >> Extracting chemically meaningful atom-in-material descriptors (net atomic >> charges, atomic spin moments, bond orders, s-p-d-f-g populations, etc.) >> carries with it the extra requirements of exhibiting correlations to >> experimental observables and of having well-defined mathematical values >> (including a complete basis set limit) and of exhibiting chemical >> consistency between various chemical descriptors. A multipole expansion of >> the Coulomb operator (such as the Mulliken-based multipole expansion you >> mentioned) has nothing to do with chemically meaningful descriptors, it is >> simply a trick to re-write the density matrix using a different basis >> representation to simplify the calculation of Coulomb integrals. In other >> words, it is merely algorithmic. >> >> The great confusion regarding Mulliken populations, which are simply >> mathematical artifices and not chemical properties, is that they have >> historically been confused with chemical properties like net atomic >> charges. Just like basis set overlap integrals, Mulliken populations can be >> a useful ingredient for expanding the Coulomb operator, as your example >> illustrates, but they are no more chemical properties of a material than >> basis set overlap integrals are chemical properties of material. In other >> words, not everything used in a quantum chemistry calculation is a chemical >> property of a material: some are just mathematical constructs whose utility >> resides in the algorithmic computation of another quantity (e.g., >> electrostatic interaction). The origin of this great confusion is that for >> small basis sets the Mulliken populations often resemble the net atomic >> charges computed by other methods, but this is somewhat coincidental >> because the correlation fails to hold when the basis set is improved. >> >> The reason this often confuses people is because there are actually two >> opposite ways to construct a polyatomic multipole expansion: >> >> (a) using quantities that are merely algorithmic (e.g., Mulliken >> populations) in the sense they have no complete basis set limit but >> none-the-less can be used as a basis representation to expand the Coulomb >> potential and >> >> (b) using chemically well-defined quantities (e.g., DDEC6 or QTAIM or >> Hirshfeld NACs and atomic multipoles) that have well-defined complete basis >> set limits and can be used as a basis representation to expand the Coulomb >> potential >> >> People often fail to recognize the distinction between these two cases, >> which have a day and night difference between them. >> >> Sincerely, >> >> Tom >> >> >> On Mon, Jun 29, 2020 at 8:43 AM Stefan Grimme grimme**thch.uni-bonn.de > ~~ ccl.net> wrote: >> >>> >>> Sent to CCL by: "Stefan Grimme" [grimme..thch.uni-bonn.de] >>> One more comment to the Mulliken charge discussion: >>> even methods without a well-defined basis set limit can be useful >>> as already mentioned by Marcel Swart. This holds >>> for the Mulliken atomic charge partitioning in compact MB/DZ basis sets >>> (even TZ is often reasonable). For example the DFTB and GFN-xTB >>> tight-binding methods are fundamentally based on a Mulliken analysis of the >>> density matrix and yield physically very reasonable electrostatic energies. >>> In GFN2-xTB this also works well up to quadrupole moments. >>> Its clear that the Mulliken scheme breaks down for AO basis sets >>> containing >>> diffuse components but I really would like to see a differentiated view >>> on the topic (and not as in a recent general statement of a reviewer >>> something like "I do not think Mulliken charges are trustworthy"). >>> Best >>> Stefan Grimme>>> E-mail to subscribers: CHEMISTRY ~~ ccl.net or use:>>> >>> E-mail to administrators: CHEMISTRY-REQUEST ~~ ccl.net or use>>> >>> >>> --000000000000df88b905a965c7cc Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Dear CCL users,

=
I find it interesting that a similar discussion on this topic has spar= ked almost simultaneously on Matter Modeling Stack Exchange

<= /div>

Of course this discussion of charge has been ongoing for many years and = also across many different forums.=C2=A0 But if you are inclined I encourag= e you to look at the current answers there and post an answer if you want t= o add more to the discussion, because this is a very important question.=C2= =A0

Best,=C2=A0
Cody Aldaz


=

On Mon, Jun 29, 2020 at 1:44 PM Thomas Manz thomasa= manz%gmail.com <owner-chemistry:_:ccl.net> wrote:
Hi Stefan,

I wanted to furthe= r clarify one aspect of my earlier response.

Suppo= se that one has a NaCl crystal, for example. Using a Mulliken population an= alysis, depending on the basis set, the populations of the Na and Cl atoms = could take on any values that sum to 11=C2=A0+ 17=C2=A0 =3D 28 electrons. F= or example, one could have 11.3488 electrons on the Na atom and 28=C2=A0 -= =C2=A0 11.3488 =3D=C2=A0 16.6512 electrons on the Cl atom. Using a different basis= set, the Mulliken population analysis might yield 10.2342 electrons on the= Na atom and 28 -=20 10.2342=20 =3D 17.7658 electrons on the Cl atom. Using another basis set, you might get 11.0000 el= ectrons on the Na atom and 28 - 11.0000 =3D 17.0000 electrons on the Cl ato= m. For any chosen basis set, the Mulliken populations (or any other kind of= populations) and their corresponding atomic multipoles and charge penetrat= ion (i.e., Coulombic electrostatic interaction between overlapping function= s) integrals could be used as a representation to expand the Coulomb operat= or (i.e., to calculate the Coulomb=C2=A0interaction between electrons in th= e quantum chemistry calculation). If the expansion is carried out to high e= nough order, then its precision could be arbitrarily high (e.g., reproduce = the Coulomb interaction to machine precision). It is very clear to see this= has nothing to do with chemically meaningful atom-in-material descriptors,= because in case 1 the Na atom in the NaCl crystal would be assigned [sic] = as an anion and the Cl atom as a cation; in case 2 the Na atom in the NaCl = crystal would be assigned [sic] as an cation and the Cl atom as a anion; an= d in case 3 the Na atom in the NaCl crystal would be assigned [sic] as neutra= l (i.e., bearing no net charge) and the Cl atom also as neutral. Hence, the= Mulliken populations cannot be net atomic charges in general.
Sincerely,

Tom

On Mon, Jun 29, 2= 020 at 9:27 AM Thomas Manz <thomasamanz ~~ gmail.com> wrote:
Hi Stefan,

I think the confusi= on arises, because the Mulliken populations are sometimes confused with net= atomic charges.

The expansion of the electron den= sity can be performed using any desired basis. In your application, the Mul= liken partitioning is just a basis representation for expanding the electro= n=C2=A0density in terms of a distributed multipole expansion (e.g., up to q= uadrupole order). Yes, the Mulliken partitioning can be a mechanism to form= ulate a distributed multipole expansion of the electron density which can b= e a useful computational algorithm for computing electrostatic interactions= during a quantum chemistry calculation. This is somewhat related to the fa= st multipole moments expansion of the Coulomb operator in quantum chemistry= calculations. But, this is an entirely different topic than extracting che= mically meaningful atom-in-material descriptors from a quantum chemistry ca= lculation.

Extracting=20 chemically meaningful atom-in-material descriptors (net atomic charges, ato= mic spin moments, bond orders, s-p-d-f-g populations, etc.) carries with it= the extra requirements of exhibiting correlations to experimental observab= les and of having well-defined mathematical values (including a complete ba= sis set limit) and of exhibiting chemical consistency between various chemi= cal descriptors. A multipole expansion of the Coulomb operator (such as the= Mulliken-based multipole expansion you mentioned) has nothing to do with c= hemically meaningful descriptors, it is simply a trick to re-write the dens= ity matrix using a different basis representation to simplify the calculati= on of Coulomb integrals. In other words, it is merely algorithmic.

The great confusion regarding Mulliken populations, which = are simply mathematical artifices and not chemical properties, is that they= have historically been confused with chemical properties like net atomic c= harges. Just like basis set overlap integrals, Mulliken populations can be = a useful ingredient for expanding the Coulomb operator, as your example ill= ustrates, but they are no more chemical properties of a material than basis= set overlap integrals are chemical properties of material. In other words,= not everything used in a quantum chemistry calculation is a chemical prope= rty of a material: some are just mathematical constructs whose utility resi= des in the algorithmic computation of another quantity (e.g., electrostatic= interaction). The origin of this great confusion is that for small basis s= ets the Mulliken populations often resemble the net atomic charges computed= by other methods, but this is somewhat coincidental because the correlatio= n fails to hold when the basis set is improved.

Th= e reason this often confuses people is because there are actually two oppos= ite ways to construct a polyatomic multipole expansion:=C2=A0
(a) using quantities that are merely algorithmic (e.g., Mullike= n populations) in the sense they have no complete basis set limit but none-= the-less can be used as a basis representation to expand the Coulomb potent= ial and=C2=A0

(b) using chemically well-defined qu= antities (e.g., DDEC6 or QTAIM or Hirshfeld NACs and atomic multipoles) tha= t have well-defined complete basis set limits and can be used as a basis re= presentation to expand the Coulomb potential=20

People often fail to recognize the distinction be= tween these two cases, which have a day and night difference between them.<= br>

Sincerely,

Tom
<= div>=C2=A0

On Mon, Jun 29, 2020 at 8:43 AM Stefan Grimme grimme**thch.uni-bonn.de <<= a href=3D"mailto:owner-chemistry+~~+ccl.net" target=3D"_blank">owner-chemis= try ~~ ccl.net> wrote:

Sent to CCL by: "Stefan=C2=A0 Grimme" [grimme..thch.uni-bonn.de= ]
One more comment to the Mulliken charge discussion:
even methods without a well-defined basis set limit can be useful
as already mentioned by Marcel Swart. This holds
for the Mulliken atomic charge partitioning in compact MB/DZ basis sets
(even TZ is often reasonable). For example the DFTB and GFN-xTB tight-bindi= ng methods are fundamentally based on a Mulliken analysis of the density ma= trix and yield physically very reasonable electrostatic energies. In GFN2-x= TB this also works well up to quadrupole moments.
Its clear that the Mulliken scheme breaks down for AO basis sets containing=
diffuse components but I really would like to see a differentiated view on = the topic (and not as in a recent general statement of a reviewer something= like "I do not think Mulliken charges are trustworthy").
Best
Stefan Grimme



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