David Mazziotti

David Mazziotti

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11 years, 6 days
I am a professor in the Department of Chemistry and the James Franck Institute at The University of Chicago. I am also the founder and principal scientific adviser at RDMChem LLC.

MaplePrimes Activity


These are answers submitted by David Mazziotti

Here is the PES of ArF for bond lengths between 2.2 and 3.6 from HartreeFock and Parametric2RDM in the cc-pVDZ basis set. 

> with(QuantumChemistry):

> mols := [seq([["Ar",0,0,0],["F",0,0,2+0.2*i]], i=1..8)];
         mols := [[["Ar", 0, 0, 0], ["F", 0, 0, 2.2]],

           [["Ar", 0, 0, 0], ["F", 0, 0, 2.4]],

           [["Ar", 0, 0, 0], ["F", 0, 0, 2.6]],

           [["Ar", 0, 0, 0], ["F", 0, 0, 2.8]],

           [["Ar", 0, 0, 0], ["F", 0, 0, 3.0]],

           [["Ar", 0, 0, 0], ["F", 0, 0, 3.2]],

           [["Ar", 0, 0, 0], ["F", 0, 0, 3.4]],

           [["Ar", 0, 0, 0], ["F", 0, 0, 3.6]]]


> energies_hf := map(Energy, mols, basis="ccpvdz");
  energies_hf := [-626.151444023726, -626.162686642662,

    -626.167860375677, -626.170173135759, -626.171174175847,

    -626.171382087638, -626.171677653194, -626.171758395594]


> energies_p2rdm := map(Energy, mols, basis="ccpvdz", method=Parametric2RDM);
  energies_p2rdm := [-626.472462673700, -626.480383384324,

    -626.483830355819, -626.485335054846, -626.485825123186,

    -626.485799957140, -626.485973310631, -626.485977743599]


> x := [seq(i[2][4], i in mols)];
         x := [2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6]

> xy_hf := [seq([x[i],energies_hf[i]], i=1..nops(x))];
 xy_hf := [[2.2, -626.151444023726], [2.4, -626.162686642662],

   [2.6, -626.167860375677], [2.8, -626.170173135759],

   [3.0, -626.171174175847], [3.2, -626.171382087638],

   [3.4, -626.171677653194], [3.6, -626.171758395594]]


> xy_p2rdm := [seq([x[i],energies_p2rdm[i]], i=1..nops(x))];
xy_p2rdm := [[2.2, -626.472462673700], [2.4, -626.480383384324],

  [2.6, -626.483830355819], [2.8, -626.485335054846],

  [3.0, -626.485825123186], [3.2, -626.485799957140],

  [3.4, -626.485973310631], [3.6, -626.485977743599]]


> plot(spline(x,energies_p2rdm,z), axes=boxed, view=[2.2..3.6,-626.47..-626.488]);

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In the Parametric2RDM PES there is a very slight increase around 3.0 Angstroms.  From your note it appears that a similar increase is present in CoupledCluster.  The PES has flattened by 3.0 Angstroms because the atoms are breaking apart.  The increase is within the error of quantum chemistry methods.  Counterpoise correction would not likely matter.

David

 

Hi -

Use:

 

LinearAlgebra:-Eigenvalues(A);

 

David

Hi,

 

You should be able to do something like:

 

fsolve( diif( f(x), x) = 0, x);

 

David

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