qstack.fields.hf_otpd¶

Hartree-Fock on-top pair density.

qstack.fields.hf_otpd.hf_otpd(mol, dm, grid_level=3, save_otpd=False, return_all=False)[source]¶

Compute the Hartree-Fock uncorrelated on-top pair density (OTPD) on a grid.

The on-top pair density is the probability density of finding two electrons at the same position. For Hartree-Fock, this is computed as (rho/2)^2.

Parameters:

mol (pyscf Mole) – pyscf Mole object.
dm (numpy ndarray) – 2D density matrix in AO-basis.
grid_level (int) – DFT grid level controlling number of radial and angular points. Defaults to 3.
save_otpd (bool) – If True, saves results to a .npz file. Defaults to False.
return_all (bool) – If True, returns both OTPD and grid object; if False, returns only OTPD. Defaults to False.

Returns:

If return_all is False, returns 1D array of OTPD values. If return_all is True, returns tuple of (otpd, grid) where grid is the pyscf Grid object.

Return type:

numpy ndarray or tuple

qstack.fields.hf_otpd.save_OTPD(mol, otpd, grid)[source]¶

Save on-top pair density computation results to a NumPy compressed file.

Creates a .npz file containing the molecular structure, OTPD values, grid coordinates, and integration weights for later analysis.

Parameters:

mol (pyscf Mole) – pyscf Mole object.
otpd (numpy ndarray) – 1D array of on-top pair density values on the grid.
grid (pyscf Grid) – Grid object containing coordinates and weights.