From owner-chemistry@ccl.net Thu Sep 3 10:54:00 2015 From: "Thomas Manz thomasamanz-,-gmail.com" To: CCL Subject: CCL: NBO vs Loewdin Charges Message-Id: <-51667-150903104633-18278-69JaSWERz465ZJqLNQzF7g ~ server.ccl.net> X-Original-From: Thomas Manz Content-Type: multipart/alternative; boundary=001a11c14836199890051ed8d9e2 Date: Thu, 3 Sep 2015 08:46:27 -0600 MIME-Version: 1.0 Sent to CCL by: Thomas Manz [thomasamanz^gmail.com] --001a11c14836199890051ed8d9e2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Victor, Sorry, I did not mean to imply that non-nuclear attractors do not exist. They do exist in some materials. The challenge that occurs is that when a non-nuclear attractor is present, it does not fulfill the goal to compute net atomic charges, since some of the electrons are assigned to the non-nuclear attractor instead of to one of the atoms. I realize there are various good reasons to perform a topological analysis of the electron density. I'm just saying that if the goal is to create a default method for assigning atomic properties, it is not the most straightforward approac= h since some of the properties may belong to the non-nuclear attractors instead of the atoms. Trying to assign the non-nuclear attractor to one of the atoms (i.e., closest atom) may not be possible without breaking the crystal symmetry (i.e., what happens if the non-nuclear attractor is located the same distance from multiple atoms? Obviously, Bader analysis has a well-defined basis set limit, since it is a functional of the electron distribution. Tom On Wed, Sep 2, 2015 at 9:04 PM, V=C3=ADctor Lua=C3=B1a Cabal victor(0) fluor.quimica.uniovi.es wrote: > > Sent to CCL by: =3D?iso-8859-1?Q?V=3DEDctor_Lua=3DF1a?=3D Cabal [victor_+= _ > fluor.quimica.uniovi.es] > On Wed, Sep 02, 2015 at 10:15:53AM -0600, Thomas Manz thomasamanz### > gmail.com wrote: > > Hi, > > > > The difficulty with charge assignment schemes is largely due to > historical > > artifacts. > > All of the earliest schemes for assigning net atomic charges were > seriously > > flawed: Mulliken, Lowden, Hirshfeld, etc. > > Even Bader's AIM theory, which has many beautiful theoretical propertie= s, > > can give non-nuclear attractors in some materials. > > The persistent use of methods like Mulliken and Lowden, which have been > > known for decades (longer than most of us have been alive) > > to be highly unstable and have no well-defined basis set limit, has > > contributed to the confusion. > > Sorry, but I *must* intervene. > > Non nuclear attractors (NNA) aka NNM (non nuclear maxima) *are real* an > have a well known meaning [6]. In my opinion hey have a "well-defined > basis set limit", but I don't really known if we agree on what that > means. Using good enough basis sets and xc treatments are essential, > and it is easy to agree on that. > > By other names NNA'shave been known as electrides [1], solved electrons > [2], color centers [3], solids under high pressure conditions [4] > ... and many other well accepted physical known properties. Many are > known since one century or more to any solid state physicists. > > It is true that the issue was plenty of confusion and wrong seminal > ideas. For instance, it proved to be wrong that metellicity was due > to the existence of NNA's. The true result is that a metal may have > NNA's (Li, Na, ...) [5] or it may not have NNA's (Cs, many 3d pure > metals ...). Metalic character and NNA are different properties, each > responding to different characteristics. > > There are other real causes to the confussion on this subject. The > carbon-carbon bond exemplifies many. In the case of triple C#C bonds > the interatomic distances are closer to the border of occurence or > not occurrence of NNA's. Details on basis set, electron correlation > treatment, embeding, ... can produce that real or spurious NNA's appear > in your calculation. My advise (and this has been given *many times* > by any good in sillico chemists: never trust an apparent software result > before examining the variables that control it). Remember the old saying: > 'garbage in garbage out' (GIGO). In the case of NNA's: explore well the > effect of the interatomic distances and then anything that influences > the geometry. > > This is a particular subject in which I have worked and published for > a long time. I hoped that the issue would be clear after Phys. Rev. Lett. > 83 (1999) 1930 [6], but I should have know best. > > Peace and success, > V=C3=ADctor > > [1] Density-functional description of electrides > SG Dale, A Otero-de-la-Roza, ER Johnson > Physical Chemistry Chemical Physics 16 (2014) 14584-14593 > > [2] Na solved in NH3 produces solved electrons that give a nice blue > color to the solution. This is explained in many general chemistry course= s > (Chemistry 101, if you prefer te USA terms). > > [3] Rigorous characterization of oxygen vacancies in ionic oxides > Paula Mori-S=C3=A1nchez et al > Phys. Rev. B 66 (2002) 075103-1--6 > > [4] Non-nuclear maxima of the electron density on alkaline metals > V Lua=C3=B1a, P Mori-S=C3=A1nchez, A Costales, MA Blanco, AM Pend=C3=A1s > The Journal of chemical physics 119 (2003) 6341-6350 > > [5] Polarity inversion in the electron density of BP crystal, > Paula Mori-S=C3=A1nchez, =C3=81ngel Mart=C3=ADn Pend=C3=A1s, V=C3=ADctor = Lua=C3=B1a > Phys. Rev. B 63 (2001) 125103-1--4 > > [6] Non-nuclear maxima of the electron density > AM Pend=C3=A1s, MA Blanco, A Costales, P Mori-S=C3=A1nchez, V Lua=C3=B1a > Physical review letters 83 (1999) 1930 > > -- > . . "In science a person can be convinced by a good argument. > / `' \ That is almost impossible in politics or religion" > /(o)(o)\ (Adapted from Carl Sagan) > /`. \/ .'\ "Lo mediocre es peor que lo bueno, pero tambi=C3=A9n es peo= r > / '`'` \ que lo malo, porque la mediocridad no es un grado, es una > | \'`'`/ | actitud" -- Jorge Wasenberg, 2015 > | |'`'`| | (Mediocre is worse than good, but it is also worse than > \/`'`'`'\/ bad, because mediocrity is not a grade, it is an attitude) > =3D=3D=3D(((=3D=3D)))=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > ! Dr.V=C3=ADctor Lua=C3=B1a, in silico chemist & prof. !"I have two kinds= of > problems, > ! Departamento de Qu=C3=ADmica F=C3=ADsica y Anal=C3=ADtica ! the urgent = and the > important. > ! Universidad de Oviedo, 33006-Oviedo, Spain ! The urgent are not > important, > ! e-mail: victor^^fluor.quimica.uniovi.es ! and the important are > never > ! phone: +34-985-103491 fax: +34-985-103125 ! urgent. > +--------------------------------------------+ (Dwight D. > Eisenhower) > GroupPage : http://azufre.quimica.uniovi.es/ > > > > -=3D This is automatically added to each message by the mailing script = =3D-> > > --001a11c14836199890051ed8d9e2 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Victor,

Sorry, I did not mean to imply = that non-nuclear attractors do not exist.
They do exist in so= me materials.
The challenge that occurs is that when a non-nuclea= r attractor is present,=C2=A0
it does not fulfill the goal to com= pute net atomic charges, since some of the
electrons are assigned= to the non-nuclear attractor instead of to one of the atoms.
I realize there are various good reasons to perform a topologic= al analysis of
the electron density. I'm just saying that if = the goal is to create a default method
for assigning atomic prope= rties, it is not the most straightforward approach
since some of = the properties may belong to the non-nuclear attractors instead of
the atoms.=C2=A0

Trying to assign the non-nuclea= r attractor to one of the atoms (i.e., closest atom)=C2=A0
may no= t be possible without breaking the crystal symmetry (i.e., what happens
if the non-nuclear attractor is located the same distance from multi= ple atoms?

Obviously, Bader analysis has a well-de= fined basis set limit, since it is a=C2=A0
functional of the elec= tron distribution.

Tom

<= div class=3D"gmail_extra">
On Wed, Sep 2, 201= 5 at 9:04 PM, V=C3=ADctor Lua=C3=B1a Cabal victor(0)fluor.quimica.uniovi.es <owner-chemistry{}ccl= .net> wrote:

Sent to CCL by: =3D?iso-8859-1?Q?V=3DEDctor_Lua=3DF1a?=3D Cabal [victor_+_<= a href=3D"http://fluor.quimica.uniovi.es" rel=3D"noreferrer" target=3D"_bla= nk">fluor.quimica.uniovi.es]
On Wed, Sep 02, 2015 at 10:15:53AM -0600, Thomas Manz thom= asamanz###gmail.com wrote:
> Hi,
>
> The difficulty with charge assignment schemes is largely due to histor= ical
> artifacts.
> All of the earliest schemes for assigning net atomic charges were seri= ously
> flawed: Mulliken, Lowden, Hirshfeld, etc.
> Even Bader's AIM theory, which has many beautiful theoretical prop= erties,
> can give non-nuclear attractors in some materials.
> The persistent use of methods like Mulliken and Lowden, which have bee= n
> known for decades (longer than most of us have been alive)
> to be highly unstable and have no well-defined basis set limit, has > contributed to the confusion.

Sorry, but I *must* intervene.

Non nuclear attractors (NNA) aka NNM (non nuclear maxima) *are real* an
have a well known meaning [6]. In my opinion hey have a "well-defined<= br> basis set limit", but I don't really known if we agree on what tha= t
means. Using good enough basis sets and xc treatments are essential,
and it is easy to agree on that.

By other names NNA'shave been known as electrides [1], solved electrons=
[2], color centers [3], solids under high pressure conditions [4]
... and many other well accepted physical known properties. Many are
known since one century or more to any solid state physicists.

It is true that the issue was plenty of confusion and wrong seminal
ideas. For instance, it proved to be wrong that metellicity was due
to the existence of NNA's. The true result is that a metal may have
NNA's (Li, Na, ...) [5] or it may not have NNA's (Cs, many 3d pure<= br> metals ...). Metalic character and NNA are different properties, each
responding to different characteristics.

There are other real causes to the confussion on this subject. The
carbon-carbon bond exemplifies many. In the case of triple C#C bonds
the interatomic distances are closer to the border of occurence or
not occurrence of NNA's. Details on basis set, electron correlation
treatment, embeding, ... can produce that real or spurious NNA's appear=
in your calculation. My advise (and this has been given *many times*
by any good in sillico chemists: never trust an apparent software result before examining the variables that control it). Remember the old saying: 'garbage in garbage out' (GIGO). In the case of NNA's: explore = well the
effect of the interatomic distances and then anything that influences
the geometry.

This is a particular subject in which I have worked and published for
a long time. I hoped that the issue would be clear after Phys. Rev. Lett. 83 (1999) 1930 [6], but I should have know best.

Peace and success,
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0V=C3= =ADctor

[1] Density-functional description of electrides
SG Dale, A Otero-de-la-Roza, ER Johnson
Physical Chemistry Chemical Physics 16 (2014) 14584-14593

[2] Na solved in NH3 produces solved electrons that give a nice blue
color to the solution. This is explained in many general chemistry courses<= br> (Chemistry 101, if you prefer te USA terms).

[3] Rigorous characterization of oxygen vacancies in ionic oxides
Paula Mori-S=C3=A1nchez et al
Phys. Rev. B 66 (2002) 075103-1--6

[4] Non-nuclear maxima of the electron density on alkaline metals
V Lua=C3=B1a, P Mori-S=C3=A1nchez, A Costales, MA Blanco, AM Pend=C3=A1s The Journal of chemical physics 119 (2003) 6341-6350

[5] Polarity inversion in the electron density of BP crystal,
Paula Mori-S=C3=A1nchez, =C3=81ngel Mart=C3=ADn Pend=C3=A1s, V=C3=ADctor Lu= a=C3=B1a
Phys. Rev. B 63 (2001) 125103-1--4

[6] Non-nuclear maxima of the electron density
AM Pend=C3=A1s, MA Blanco, A Costales, P Mori-S=C3=A1nchez, V Lua=C3=B1a Physical review letters 83 (1999) 1930

--
=C2=A0 =C2=A0 =C2=A0.=C2=A0 .=C2=A0 =C2=A0 "In science a person can be= convinced by a good argument.
=C2=A0 =C2=A0 / `' \=C2=A0 =C2=A0That is almost impossible in politics = or religion"
=C2=A0 =C2=A0/(o)(o)\=C2=A0 (Adapted from Carl Sagan)
=C2=A0 /`. \/ .'\=C2=A0 "Lo mediocre es peor que lo bueno, pero ta= mbi=C3=A9n es peor
=C2=A0/=C2=A0 =C2=A0'`'`=C2=A0 =C2=A0\ que lo malo, porque la medio= cridad no es un grado, es una
=C2=A0|=C2=A0 \'`'`/=C2=A0 | actitud" -- Jorge Wasenberg, 2015=
=C2=A0|=C2=A0 |'`'`|=C2=A0 | (Mediocre is worse than good, but it i= s also worse than
=C2=A0 \/`'`'`'\/=C2=A0 bad, because mediocrity is not a grade,= it is an attitude)
=3D=3D=3D(((=3D=3D)))=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D+=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
! Dr.V=C3=ADctor Lua=C3=B1a, in silico chemist & prof. !"I = have two kinds of problems,
! Departamento de Qu=C3=ADmica F=C3=ADsica y Anal=C3=ADtica ! the urgent an= d the important.
! Universidad de Oviedo, 33006-Oviedo, Spain ! The urgent are not important= ,
! e-mail:=C2=A0 =C2=A0victor^^fluor.quimica.uniovi.es=C2=A0 =C2=A0= ! and the important are never
! phone: +34-985-10= 3491=C2=A0 fax: +34-985-103125 ! urgent.
+--------------------------------------------+=C2=A0 =C2=A0 =C2=A0 =C2=A0 (= Dwight D. Eisenhower)
=C2=A0GroupPage : http://azufre.quimica.uniovi.es/



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