From owner-chemistry@ccl.net Fri Jan 24 06:30:00 2014 From: "Marcel Swart marcel.swart[#]icrea.cat" To: CCL Subject: CCL: negative values in Mulliken spin distribution Message-Id: <-49604-140124062714-27305-YpXHWVMRq+F54Ur+Cz4CTA,server.ccl.net> X-Original-From: Marcel Swart Content-Type: multipart/alternative; boundary="Apple-Mail=_BC1A06E4-491C-4814-BF7C-E27637344544" Date: Fri, 24 Jan 2014 12:27:03 +0100 Mime-Version: 1.0 (Mac OS X Mail 7.1 \(1827\)) Sent to CCL by: Marcel Swart [marcel.swart++icrea.cat] --Apple-Mail=_BC1A06E4-491C-4814-BF7C-E27637344544 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Susi, we=92re saying the same thing, *but* with one big difference. The probability density you talk about leads to a Mulliken population analysis, be it the total or separated for spin-up and spin-down. Like I said, this population analysis is a=20 representation of the charge density, which are (usually) being assigned to atoms. Whether you take the total charge, or the difference between alfa- and beta-populations is to get =93spin-density charges=94 is irrelevant for the concept of how you get from the density to the atomic populations. There are many different ways how to get from a charge density to an atomic population analysis, of which Mulliken is one choice. But these atomic populations (and hence the Mulliken (spin) charges) DO directly give a representation of the charge density; how well it represents it is another issue. That was my (maybe too subtle) point. Marcel On 23 Jan 2014, at 19:27 , Susi Lehtola = susi.lehtola_._alumni.helsinki.fi wrote: >> First of all, to set things straight, it is a simplification of the >> charge density, which are being assigned to atoms. Hence, >> yes, it is not a real density. >=20 > No, it is not. You're mixing concepts. Mulliken charges and Mulliken > spin charges are not the same thing. The first deals with > electric charge, while the second deals with spin. (Also, I was > talking about a probability density, which is always non-negative.) >=20 > In the former you substract electronic charge from the nuclear > charge to get the net atomic charge. For instance, O in H2O has a > negative charge due to a relative surplus of electrons. (Here, > different methods give a variety of different answers, for example > L=F6wdin can assign O to be positive!) >=20 > In the latter you substract the amount of spin down electrons from the > amount of spin up electrons. The value 0 will mean that there are an > equal amount of spin up and down electrons for the atom. A positive > value will mean that spin up electrons are in surplus for the atom, > while a negative value will mean that spin down electrons are in > surplus. >=20 > If you calculate a spin polarized system, e.g. the oxygen molecule = with > spin multiplicity M=3D3, you'll have a net positive spin charge in the > system, since you'll have two more spin up electrons than spin down > electrons. Here, both oxygen atoms will have spin charge +1, although > the electric charge is 0. >=20 > On the other hand, even spin neutral systems may have atoms with large > negative and large positive charges, e.g. in the case of > antiferromagnetic couplings between atoms. =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 Prof. Dr. Marcel Swart ICREA Research Professor at Institut de Qu=EDmica Computacional i Cat=E0lisi Universitat de Girona Facultat de Ci=E8ncies Campus Montilivi 17071 Girona Catalunya (Spain) tel +34-972-418861 fax +34-972-418356 e-mail marcel.swart ~~ icrea.cat marcel.swart ~~ udg.edu web http://www.marcelswart.eu vCard addressbook://www.marcelswart.eu/MSwart.vcf =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 --Apple-Mail=_BC1A06E4-491C-4814-BF7C-E27637344544 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Susi,

we=92re saying the same = thing, *but* with one big difference.
The probability density = you talk about leads to a Mulliken
population analysis, be it = the total or separated for spin-up
and spin-down. Like I said, = this population analysis is a 
representation of the = charge density, which are (usually)
being assigned to atoms. = Whether you take the total charge,
or the difference between = alfa- and beta-populations is to
get =93spin-density charges=94 = is irrelevant for the concept of
how you get from the density = to the atomic populations.
There are many different ways how = to get from a charge
density to an atomic population analysis, = of which Mulliken
is one choice. But these atomic populations = (and hence
the Mulliken (spin) charges) DO directly give a = representation
of the charge density; how well it represents = it is another issue.
That was my (maybe too subtle) = point.

Marcel

On 23 Jan = 2014, at 19:27 , Susi Lehtola susi.lehtola_._alumni.helsinki.fi <owner-chemistry ~~ ccl.net> = wrote:

First of all, to set things = straight, it is a simplification of the
charge density, which are = being assigned to atoms. Hence,
yes, it is not a real = density.

No, it is not. You're mixing concepts. = Mulliken charges and Mulliken
spin charges are not the same thing. = The first deals with
electric charge, while the second deals with = spin. (Also, I was
talking about a probability density, which is = always non-negative.)

In the former you substract electronic = charge from the nuclear
charge to get the net atomic charge. For = instance, O in H2O has a
negative charge due to a relative surplus of = electrons. (Here,
different methods give a variety of different = answers, for example
L=F6wdin can assign O to be positive!)

In = the latter you substract the amount of spin down electrons from = the
amount of spin up electrons. The value 0 will mean that there are = an
equal amount of spin up and down electrons for the atom. A = positive
value will mean that spin up electrons are in surplus for = the atom,
while a negative value will mean that spin down electrons = are in
surplus.

If you calculate a spin polarized system, e.g. = the oxygen molecule with
spin multiplicity M=3D3, you'll have a net = positive spin charge in the
system, since you'll have two more spin = up electrons than spin down
electrons. Here, both oxygen atoms will = have spin charge +1, although
the electric charge is 0.

On the = other hand, even spin neutral systems may have atoms with = large
negative and large positive charges, e.g. in the case = of
antiferromagnetic couplings between = atoms.


=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
Prof= . Dr. Marcel Swart

ICREA Research Professor at
Institut de = Qu=EDmica Computacional i Cat=E0lisi
Universitat de = Girona

Facultat de Ci=E8ncies
Campus Montilivi
17071 Girona
Catalunya = (Spain)

tel
+34-972-418861
fax
+34-972-418356
e-mailmarcel.swart ~~ icrea.cat
marce= l.swart ~~ udg.edu
web
http://www.marcelswart.eu

vCard
addressbook://www.mar= celswart.eu/MSwart.vcf
=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

= --Apple-Mail=_BC1A06E4-491C-4814-BF7C-E27637344544-- From owner-chemistry@ccl.net Fri Jan 24 11:58:00 2014 From: "Fedor Goumans goumans%x%scm.com" To: CCL Subject: CCL: ADF in HPC Message-Id: <-49605-140124033202-28816-iDwhpjLhhjG4vdjdCiWwBw~~server.ccl.net> X-Original-From: Fedor Goumans Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Fri, 24 Jan 2014 09:31:45 +0100 MIME-Version: 1.0 Sent to CCL by: Fedor Goumans [goumans]=[scm.com] Dear May Abdelghani, Are you looking for ADF on French HPC centers? CINES: http://www.cines.fr/spip.php?article855&lang=fr IDRIS: http://www.idris.fr/ada/logiciels/ada-adf.html Best wishes, Fedor On 1/23/2014 10:22 PM, may abdelghani may01dz]~[yahoo.fr wrote: > Sent to CCL by: "may abdelghani" [may01dz.:.yahoo.fr] > Dear CCL'ers > I look for a high-performance computing clusters that contains the Amsterdam density functional (ADF) program > thanks> > -- Dr. T. P. M. (Fedor) Goumans Business Developer Scientific Computing & Modelling NV (SCM) Vrije Universiteit, FEW, Theoretical Chemistry De Boelelaan 1083 1081 HV Amsterdam, The Netherlands T +31 20 598 7625 F +31 20 598 7629 E-mail: goumans .. scm.com http://www.scm.com