From owner-chemistry@ccl.net Sun Jul 2 10:50:00 2017 From: "Andrew Scott Rosen rosen^u.northwestern.edu" To: CCL Subject: CCL:G: Unrestricted vs. restricted DFT for closed-shell metal complex Message-Id: <-52866-170702005700-21202-tkhyhQDSe/8dvY8UTYIxkA|-|server.ccl.net> X-Original-From: "Andrew Scott Rosen" Date: Sun, 2 Jul 2017 00:56:59 -0400 Sent to CCL by: "Andrew Scott Rosen" [rosen]^[u.northwestern.edu] Hello, I have a question regarding the choice of unrestricted versus restricted calculations in DFT. Let's say that I am dealing with a Cu(I) organometallic complex that I anticipate would have a spin multiplicity of 1 due to the assumed [Ar]3d10 electron configuration of Cu(I) in this complex. Under this assumption, the system is not open-shell. As such, it seems that a restricted calculation would be most appropriate. Would there be any benefit in running an unrestricted calculation (still as a singlet) in this case? Additionally, what would an unrestricted calculation on a system that's a singlet even mean, especially if I don't use specific keywords (e.g. in Gaussian) to try and obtain a broken- symmetry state? To provide context, I ask because I start with a Cu(II) complex that reduces to a Cu(I) complex. I do an unrestricted calculation when modeling the Cu(II) complex, and I want to compute the energy of the resulting Cu(I) complex for comparison. Thank you greatly for any input. Best regards, Andrew From owner-chemistry@ccl.net Sun Jul 2 13:35:00 2017 From: "Thomas Manz thomasamanz]*[gmail.com" To: CCL Subject: CCL:G: Unrestricted vs. restricted DFT for closed-shell metal complex Message-Id: <-52867-170702133259-18949-EGc2wYxPiHWaomM+GZ8eQg-*-server.ccl.net> X-Original-From: Thomas Manz Content-Type: multipart/alternative; boundary="f403045f57da41ebc60553590aa5" Date: Sun, 2 Jul 2017 11:32:52 -0600 MIME-Version: 1.0 Sent to CCL by: Thomas Manz [thomasamanz%a%gmail.com] --f403045f57da41ebc60553590aa5 Content-Type: text/plain; charset="UTF-8" Hi Andrew, For singlet state, the restricted and unrestricted calculations converge to the same answer if all of the electrons are paired (i.e., closed-shell singlet). For singlet state, the restricted and unrestricted calculations converge to a different answer only if the singlet is open-shell (e.g., anti-ferromagnetic states, etc.). Tom On Sat, Jul 1, 2017 at 10:56 PM, Andrew Scott Rosen rosen^u.northwestern.edu wrote: > > Sent to CCL by: "Andrew Scott Rosen" [rosen]^[u.northwestern.edu] > Hello, > > I have a question regarding the choice of unrestricted versus restricted > calculations in DFT. Let's say that I am dealing with a Cu(I) > organometallic complex that I anticipate would have a spin multiplicity of > 1 due to the assumed [Ar]3d10 electron configuration of Cu(I) in this > complex. Under this assumption, the system is not open-shell. As such, it > seems that a restricted calculation would be most appropriate. > > Would there be any benefit in running an unrestricted calculation (still as > a singlet) in this case? Additionally, what would an unrestricted > calculation on a system that's a singlet even mean, especially if I don't > use specific keywords (e.g. in Gaussian) to try and obtain a broken- > symmetry state? > > To provide context, I ask because I start with a Cu(II) complex that > reduces to a Cu(I) complex. I do an unrestricted calculation when modeling > the Cu(II) complex, and I want to compute the energy of the resulting Cu(I) > complex for comparison. > > Thank you greatly for any input. > > Best regards, > Andrew> > > --f403045f57da41ebc60553590aa5 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi Andrew,

For singlet state, the restr= icted and unrestricted calculations converge to the same answer if all of t= he electrons are paired (i.e., closed-shell singlet).
For singlet= state, the restricted and unrestricted calculations converge to a differen= t answer only if the singlet is open-shell (e.g., anti-ferromagnetic states= , etc.).

Tom

<= div class=3D"gmail_quote">On Sat, Jul 1, 2017 at 10:56 PM, Andrew Scott Ros= en rosen^u.northwestern.edu <owner-chemistry(-)ccl.net> wrote:

Sent to CCL by: "Andrew Scott Rosen" [rosen]^[u.northwestern.edu<= /a>]
Hello,

I have a question regarding the choice of unrestricted versus restricted calculations in DFT. Let's say that I am dealing with a Cu(I)
organometallic complex that I anticipate would have a spin multiplicity of<= br> 1 due to the assumed [Ar]3d10 electron configuration of Cu(I) in this
complex. Under this assumption, the system is not open-shell. As such, it seems that a restricted calculation would be most appropriate.

Would there be any benefit in running an unrestricted calculation (still as=
a singlet) in this case? Additionally, what would an unrestricted
calculation on a system that's a singlet even mean, especially if I don= 't
use specific keywords (e.g. in Gaussian) to try and obtain a broken-
symmetry state?

To provide context, I ask because I start with a Cu(II) complex that
reduces to a Cu(I) complex. I do an unrestricted calculation when modeling<= br> the Cu(II) complex, and I want to compute the energy of the resulting Cu(I)=
complex for comparison.

Thank you greatly for any input.

Best regards,
Andrew



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--f403045f57da41ebc60553590aa5-- From owner-chemistry@ccl.net Sun Jul 2 17:58:01 2017 From: "Susi Lehtola susi.lehtola/./alumni.helsinki.fi" To: CCL Subject: CCL:G: Unrestricted vs. restricted DFT for closed-shell metal complex Message-Id: <-52868-170702143442-5621-rVXS/CMhu+mEWmFn4fN7qA*server.ccl.net> X-Original-From: Susi Lehtola Content-Language: en-US Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=utf-8; format=flowed Date: Sun, 2 Jul 2017 11:34:28 -0700 MIME-Version: 1.0 Sent to CCL by: Susi Lehtola [susi.lehtola,alumni.helsinki.fi] On 07/01/2017 09:56 PM, Andrew Scott Rosen rosen^u.northwestern.edu wrote: > > Sent to CCL by: "Andrew Scott Rosen" [rosen]^[u.northwestern.edu] > Hello, > > I have a question regarding the choice of unrestricted versus restricted > calculations in DFT. Let's say that I am dealing with a Cu(I) > organometallic complex that I anticipate would have a spin multiplicity of > 1 due to the assumed [Ar]3d10 electron configuration of Cu(I) in this > complex. Under this assumption, the system is not open-shell. As such, it > seems that a restricted calculation would be most appropriate. > > Would there be any benefit in running an unrestricted calculation (still as > a singlet) in this case? Additionally, what would an unrestricted > calculation on a system that's a singlet even mean, especially if I don't > use specific keywords (e.g. in Gaussian) to try and obtain a broken- > symmetry state? If you run spin-unrestricted DFT with a spin-restricted guess, you'll get the same solution as with spin-restricted DFT, only getting it will be 2-3x more expensive. This is because there's nothing that will break the alpha-beta spin symmetry: a restricted guess gives identical alpha and beta Fock matrices, and consecutively identical new alpha and beta orbitals. -- ----------------------------------------------------------------------- Mr. Susi Lehtola, PhD Chemist Postdoctoral Fellow susi.lehtola##alumni.helsinki.fi Lawrence Berkeley National Laboratory http://www.helsinki.fi/~jzlehtol USA ----------------------------------------------------------------------- From owner-chemistry@ccl.net Sun Jul 2 21:45:00 2017 From: "Thomas Manz thomasamanz!A!gmail.com" To: CCL Subject: CCL:G: Unrestricted vs. restricted DFT for closed-shell metal complex Message-Id: <-52869-170702210739-11516-wlj79LMFI3trGquUo5V6aQ!=!server.ccl.net> X-Original-From: Thomas Manz Content-Type: multipart/alternative; boundary="001a114434a0446e5e05535f647a" Date: Sun, 2 Jul 2017 19:07:32 -0600 MIME-Version: 1.0 Sent to CCL by: Thomas Manz [thomasamanz/./gmail.com] --001a114434a0446e5e05535f647a Content-Type: text/plain; charset="UTF-8" Hi, If you want to break the alpha-beta symmetry, use Guess=Mix. Tom On Sun, Jul 2, 2017 at 12:34 PM, Susi Lehtola susi.lehtola/./ alumni.helsinki.fi wrote: > > Sent to CCL by: Susi Lehtola [susi.lehtola,alumni.helsinki.fi] > On 07/01/2017 09:56 PM, Andrew Scott Rosen rosen^u.northwestern.edu wrote: > >> >> Sent to CCL by: "Andrew Scott Rosen" [rosen]^[u.northwestern.edu] >> Hello, >> >> I have a question regarding the choice of unrestricted versus restricted >> calculations in DFT. Let's say that I am dealing with a Cu(I) >> organometallic complex that I anticipate would have a spin multiplicity of >> 1 due to the assumed [Ar]3d10 electron configuration of Cu(I) in this >> complex. Under this assumption, the system is not open-shell. As such, it >> seems that a restricted calculation would be most appropriate. >> >> Would there be any benefit in running an unrestricted calculation (still >> as >> a singlet) in this case? Additionally, what would an unrestricted >> calculation on a system that's a singlet even mean, especially if I don't >> use specific keywords (e.g. in Gaussian) to try and obtain a broken- >> symmetry state? >> > If you run spin-unrestricted DFT with a spin-restricted guess, you'll get > the same solution as with spin-restricted DFT, only getting it will be 2-3x > more expensive. This is because there's nothing that will break the > alpha-beta spin symmetry: a restricted guess gives identical alpha and beta > Fock matrices, and consecutively identical new alpha and beta orbitals. > -- > ----------------------------------------------------------------------- > Mr. Susi Lehtola, PhD Chemist Postdoctoral Fellow > susi.lehtola a 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/> > > --001a114434a0446e5e05535f647a Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi,=C2=A0

If you want to break the alph= a-beta symmetry, use Guess=3DMix.

Tom

On Sun, Jul 2, 2017 at 1= 2:34 PM, Susi Lehtola susi.lehtola/./= alumni.helsinki.fi <owner-chemistry]^[ccl.net> wrote= :

Sent to CCL by: Susi Lehtola [susi.lehtola,alumni.helsinki.fi]
On 07/01/2017 09:56 PM, Andrew Scott Rosen rosen^u.northwestern.edu wro= te:

Sent to CCL by: "Andrew Scott Rosen" [rosen]^[u.northwestern.edu<= /a>]
Hello,

I have a question regarding the choice of unrestricted versus restricted calculations in DFT. Let's say that I am dealing with a Cu(I)
organometallic complex that I anticipate would have a spin multiplicity of<= br> 1 due to the assumed [Ar]3d10 electron configuration of Cu(I) in this
complex. Under this assumption, the system is not open-shell. As such, it seems that a restricted calculation would be most appropriate.

Would there be any benefit in running an unrestricted calculation (still as=
a singlet) in this case? Additionally, what would an unrestricted
calculation on a system that's a singlet even mean, especially if I don= 't
use specific keywords (e.g. in Gaussian) to try and obtain a broken-
symmetry state?
If you run spin-unrestricted DFT with a spin-restricted guess, you'll g= et the same solution as with spin-restricted DFT, only getting it will be 2= -3x more expensive. This is because there's nothing that will break the= alpha-beta spin symmetry: a restricted guess gives identical alpha and bet= a Fock matrices, and consecutively identical new alpha and beta orbitals. --
-----------------------------------------------------------------= ------
Mr. Susi Lehtola, PhD=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Chemis= t Postdoctoral Fellow
susi.lehtola a alumni.helsinki.fi=C2=A0 =C2=A0Lawrence Berkeley Nationa= l Laboratory
http://www.helsinki.fi/~jzlehtol=C2=A0 USA
-----------------------------------------------------------------= ------



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