CCL: BSSE Counterpoise correction



 Sent to CCL by: Tobias Kraemer [Tobias.Kraemer{}mu.ie]
 Hi,
 Yes, CP corrections should be beformed on both the transition state (since this
 can be considered a supermolecule made of two fragments A and B) and the bonded
 addition product AB. For the individual fragments A and B you don't need and CP
 correction, it would in fact be
 difficult to do so anyways. You need knowledge of the position of both fragments
 for this type of calculation, and for the isolated fragments you don't have this
 information. The BSSE does not come into effect here.
 Tobias
 Dr. Tobias Krämer
 Lecturer in Inorganic Chemistry
 Department of Chemistry
 Maynooth University, Maynooth, Co. Kildare, Ireland.
 E: tobias.kraemer%x%mu.ie   T: +353 (0)1 474 7517
 -----Original Message-----
 > From: owner-chemistry+tobias.kraemer==mu.ie%x%ccl.net
 <owner-chemistry+tobias.kraemer==mu.ie%x%ccl.net> On Behalf Of Lee Jones
 bunglinpie---googlemail.com
 Sent: 01 July 2019 09:28
 To: Tobias Kraemer <Tobias.Kraemer%x%mu.ie>
 Subject: CCL: BSSE Counterpoise correction
 Sent to CCL by: "Lee  Jones" [bunglinpie**googlemail.com] Hi
 Thanks for your reply.
 I think I have it now, but just to make sure i'm following you correctly, I
 should perform CP correction calculations on the Transition state AB* and the
 bonded addition product AB, but would calculate the energies of the individual
 reactants A and B in the normal way without any CP corrections?
 Is it best to perform a geometry optimisation+freq with CP correction active, or
 should I optimise first, then perform a single point CP correction on the
 optimised structure?  The basis set size can have an effect on the geometry and
 frequencies so I guess it would make sense for CP to be active throughout.
 Thanks
 > "Antarip Halder antarip.halder:_:gmail.com"  wrote:
 >
 > Sent to CCL by: Antarip Halder [antarip.halder++gmail.com]
 > --000000000000a2e42d058c6e9ce7
 > Content-Type: text/plain; charset="UTF-8"
 >
 > Hi,
 >
 > BSSE comes into picture when you want to calculate the interaction
 > energy of a molecular assembly (say XY). Interaction energy of a
 > molecular assembly is defined as electronic energy of the complete
 > assembly XY
 (E_XY)
 > minus the sum of the electronic energies of individual monomer (E_X +
 E_Y).
 > The problem is, to construct the wave function for XY we use more
 > number
 of
 > basis set functions than for X or Y. Therefore, the energy difference
 (E_XY
 > - E_X -E_Y) gets overestimated. All the three energies should be
 calculated
 > using same number number of basis set functions and that is taken care
 > of by the counterpoise method.
 >
 > Now in your case, if you want to find out the correct interaction
 > energy
 of
 > the bio-molecular assembly AB then run CP calculation on AB to get the
 BSSE
 > correction (say E_BSSE). So your final interaction energy should be,
 > E_AB
 -
 > E_A - E_B + E_BSSE. Similarly if you are interested to find out how
 stable
 > your intermediate (AB)* is, then calculate its interaction energy as,
 > E_(AB)* - E_A - E_B + E*_BSSE. Here E*_BSSE is the correction energy
 > obtained from the counterpoise calculation performed on (AB)*.
 >
 > Hope this helps.
 >
 > Thanks,
 > Antarip
 >
 > On Sat, Jun 29, 2019 at 5:01 AM Lee Jones bunglinpie[*]googlemail.com
 > < owner-chemistry]~[ccl.net> wrote:
 >
 > >
 > > Sent to CCL by: "Lee  Jones" [bunglinpie|,|googlemail.com]
 Hi.  I'm
 > > after a little guidance regarding Basis Set Superposition
 Error.
 > >
 > > I understand what BSSE is and how to perform a counterpoise
 > > correction using ghost atoms, but my question is a little more
 fundamental.
 > >
 > > Considering a bimolecular addition reaction where you have reactants
 > > A and B that proceed to form a single molecule AB via a transition
 > > state AB*, what species do you actually perform the CP correction on?
 > >
 > > I read the following article which contains the following passage:
 > >
 > > https://scicomp.stackexchange.com/questions/3/what-is-counterpoise-
 > > correction
 > >
 > > "This correction will depend on the geometries of the reactants.
 > > When they are very far from one another, it will be very small: they
 > > don't influence one another. When they are very close, this effect
 > > will be small, for the same reasoning. It's the intermediate
 > > distances that
 have
 > > the largest BSSE. These are the distances at or approaching the
 > > transition state, which serves as the bottleneck for the reaction.
 > > If
 you
 > > are not accounting for the artificial improvement near the
 > > transition state, then you will get an incorrect approximation of
 > > the activation energy, the energy difference between this transition
 > > state and the separated-reactant limit."
 > >
 > >
 > > This seems to suggest that, to a first approximation, I would only
 > > need to CP correct the transition state AB* and can effectively
 > > ignore BSSE for the reactants A and B at infinite distance and for
 > > the final
 product
 > > AB (i.e. the BSSE only has a small effect on the overall reaction
 > > energy/enthalpy) is this correct.
 > >
 > >
 > > Thanks>
 > >
 > >
 >
 > --
 > If you think you can, you are right.
 >
 > --000000000000a2e42d058c6e9ce7
 > Content-Type: text/html; charset="UTF-8"
 > Content-Transfer-Encoding: quoted-printable
 >
 > <div
 dir=3D"ltr"><div>Hi,</div><div><br></div><div>BSSE
 comes into
 picture =
 > when you want to calculate the interaction energy of a molecular
 > assembly
 (=
 > say XY). Interaction energy of a molecular assembly is defined as
 electroni=
 > c energy of the complete assembly XY (E_XY) minus the sum of the
 electronic=
 >  energies of individual monomer (E_X + E_Y). The problem is, to
 > construct
 t=
 > he wave function for XY we use more number of basis set functions than
 for =
 > X or Y. Therefore, the energy difference (E_XY - E_X -E_Y) gets
 overestimat=
 > ed. All the three energies should be calculated using same number
 > number
 of=
 >  basis set functions and that is taken care of by the counterpoise
 method.<=
 > /div><div><br></div><div>Now in your case, if
 you want to find out the
 corr=
 > ect interaction energy of the bio-molecular assembly AB then run CP
 calcula=
 > tion on AB to get the BSSE correction (say E_BSSE). So your final
 interacti=
 > on energy should be, E_AB - E_A - E_B + E_BSSE. Similarly if you are
 intere=
 > sted to find out how stable your intermediate (AB)* is, then calculate
 its =
 > interaction energy as, E_(AB)* - E_A - E_B + E*_BSSE. Here E*_BSSE is
 > the
 c=
 > orrection energy obtained from the counterpoise calculation performed
 > on
 (A=
 > B)*.</div><div><br></div><div>Hope this
 helps.</div><div><br></div>
 <div>Tha=
 >
 nks,</div><div>Antarip<br></div></div><br><div
 > class=3D"gmail_quote"><div
 d=
 > ir=3D"ltr" class=3D"gmail_attr">On Sat, Jun 29, 2019
 at 5:01 AM Lee
 > Jones
 b=
 > unglinpie[*]<a href=3D"http://googlemail.com";>googlemail.com</a>
 > &lt;<a
 hre=
 > f=3D"mailto:owner-chemistry]~[ccl.net";>owner-chemistry]~[ccl.net</a>&g
 > t;
 wrote:=
 > <br></div><blockquote class=3D"gmail_quote"
 style=3D"margin:0px 0px
 > 0px
 0.8=
 > ex;border-left:1px solid
 rgb(204,204,204);padding-left:1ex"><br>
 > Sent to CCL by: &quot;Lee=C2=A0 Jones&quot; [bunglinpie|,|<a
 href=3D"http:/=
 > /googlemail.com" rel=3D"noreferrer"
 > target=3D"_blank">googlemail.com</a>]
 <b=
 > r>
 > Hi.=C2=A0 I&#39;m after a little guidance regarding Basis Set
 Superposition=
 >  Error.<br>
 > <br>
 > I understand what BSSE is and how to perform a counterpoise correction
 <br>
 > using ghost atoms, but my question is a little more fundamental.<br>
 > <br> Considering a bimolecular addition reaction where you have
 > reactants A
 <br>
 > and B that proceed to form a single molecule AB via a transition state
 <br>
 > AB*, what species do you actually perform the CP correction on?<br>
 > <br> I read the following article which contains the following
 > passage:<br> <br> <a
 > href=3D"https://scicomp.stackexchange.com/questions/3/what-is-
 counterpoi=
 > se-" rel=3D"noreferrer"
 target=3D"_blank">https://scicomp.stackexchange.com=
 > /questions/3/what-is-counterpoise-</a><br>
 > correction<br>
 > <br>
 > &quot;This correction will depend on the geometries of the reactants.
 When =
 > <br>
 > they are very far from one another, it will be very small: they
 > don&#39;t
 <=
 > br>
 > influence one another. When they are very close, this effect will be
 > <br> small, for the same reasoning. It&#39;s the intermediate
 > distances that
 hav=
 > e <br>
 > the largest BSSE. These are the distances at or approaching the <br>
 > transition state, which serves as the bottleneck for the reaction. If
 > you
 <=
 > br>
 > are not accounting for the artificial improvement near the transition
 <br>
 > state, then you will get an incorrect approximation of the activation
 <br>
 > energy, the energy difference between this transition state and the
 > <br> separated-reactant limit.&quot;<br> <br>
 <br> This seems to
 > suggest that, to a first approximation, I would only need
 <br=
 > >
 > to CP correct the transition state AB* and can effectively ignore BSSE
 <br>
 > for the reactants A and B at infinite distance and for the final
 > product
 <b=
 > r>
 > AB (i.e. the BSSE only has a small effect on the overall reaction
 <br>
 > energy/enthalpy) is this correct.<br>
 > <br>
 > <br>
 > Thanks<br>
 > <br>
 > <br>
 > <br>
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 clear=3D"all"><br>-- <br><div dir=3D"ltr"
 class=3D"g=
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 right.<br></div>
 >
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