CCL: BSSE Counterpoise correction
- From: "Lee Jones" <bunglinpie^googlemail.com>
- Subject: CCL: BSSE Counterpoise correction
- Date: Mon, 1 Jul 2019 04:27:51 -0400
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> <<a
hre=
> f=3D"mailto:owner-chemistry]~[ccl.net";>owner-chemistry]~[ccl.net</a>>
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: "Lee=C2=A0 Jones" [bunglinpie|,|<a
href=3D"http:/=
> /googlemail.com" rel=3D"noreferrer"
target=3D"_blank">googlemail.com</a>]
<b=
> r>
> Hi.=C2=A0 I'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>
> "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't
<=
> br>
> influence one another. When they are very close, this effect will be
<br>
> small, for the same reasoning. It'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."<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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> </blockquote></div><br
clear=3D"all"><br>-- <br><div dir=3D"ltr"
class=3D"g=
> mail_signature">If you think you can, you are
right.<br></div>
>
> --000000000000a2e42d058c6e9ce7--
>
>