/ HartreeFock Public

A program implementing the Hartree–Fock (also post-HF: MP2, CCSD(T), CIS and TDHF/RPA)/self-consistent field method (also DIIS) with Gaussian orbitals

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# aromanro/HartreeFock

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# HartreeFock

A program implementing the Hartree–Fock/self-consistent field method (and more, see the README at the end)

Description is available here: http://compphys.go.ro/the-hartree-fock-program/

Some Hartree-Fock theory here: http://compphys.go.ro/the-hartree-fock-method/

Some things more general (Schrödinger equation, Born-Oppenheimer approximation, variational principle), here: http://compphys.go.ro/how-to-solve-a-quantum-many-body-problem/

### HOW TO COMPUTE

Here are some things about usage:

Using the classes should be easy. Here is how to grab some atoms from the 'basis':

```	Systems::AtomWithShells H1, H2, O, N, C, He, Li, Ne, Ar;

for (auto &atom : basis.atoms)
{
if (atom.Z == 1) H1 = H2 = atom;
else if (atom.Z == 2) He = atom;
else if (atom.Z == 3) Li = atom;
else if (atom.Z == 8) O = atom;
else if (atom.Z == 6) C = atom;
else if (atom.Z == 7) N = atom;
else if (atom.Z == 10) Ne = atom;
else if (atom.Z == 18) Ar = atom;
}```

Here is how to set the H2O molecule with the coordinates from the 'Mathematica Journal' (referenced in the code):

```	H1.position.X = H2.position.X = O.position.X = 0;

H1.position.Y = 1.43233673;
H1.position.Z = -0.96104039;
H2.position.Y = -1.43233673;
H2.position.Z = -0.96104039;

O.position.Y = 0;
O.position.Z = 0.24026010;

Systems::Molecule H2O;

H2O.atoms.push_back(H1);
H2O.atoms.push_back(H2);
H2O.atoms.push_back(O);

H2O.Init();```

And here is how you calculate:

```HartreeFock::RestrictedHartreeFock HartreeFockAlgorithm;
HartreeFockAlgorithm.alpha = 0.5;
HartreeFockAlgorithm.initGuess = 0;

HartreeFockAlgorithm.Init(&H2O);
double result = HartreeFockAlgorithm.Calculate();```

You can do computation for a single atom, too, for now by putting it into a dummy molecule with a single atom in it. For example for He:

```  Systems::Molecule Heatom;
Heatom.atoms.push_back(He);
Heatom.Init();```

I added more basis sets, it's not limited to STO-nG. While doing that, I found and fixed a bug in the integrals repository that manifested for orbitals having L > 1. Now it seems to work fine.

• Split valence orbitals: 3-21G, 6-21G, 6-31G
• Besides 'split valence', polarization on heavy atoms: 6-31G*
• 'Split valence', polarization on heavy atoms and hydrogen and diffusion functions on heavy atoms: 6-31+G**

You may add more of them, the parsed format is nwchem.

### Tutorials from Crawford Group

Most of those are already implemented:

https://github.com/CrawfordGroup/ProgrammingProjects

Projects for MP2, DIIS, CCSD(T), CIS and TDHF/RPA are implemented. DIIS and MP2 are implemented for both the restricted and unrestricted methods.

Projects 1 and 2 are not implemented here, maybe I'll add a python workbook for those in the python repository, 3 was already implemented obviously before finding this. Project 7 is also not implemented, also 9 and 13.

A program implementing the Hartree–Fock (also post-HF: MP2, CCSD(T), CIS and TDHF/RPA)/self-consistent field method (also DIIS) with Gaussian orbitals

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