Shell

Represents a contracted Gaussian basis shell.

Constructor

Shell(nprim, l, pure, alpha, coeff, origin, normalize=True)

Parameters

nprim (int) — number of primitive Gaussians.
l (int) — angular momentum quantum number (0=s, 1=p, 2=d, …).
pure (bool) — True for spherical harmonics, False for Cartesian.
alpha (list[float]) — Gaussian exponents.
coeff (list[float]) — contraction coefficients.
origin (list[float]) — center coordinates [x, y, z] (Bohr).
normalize (bool, optional) — normalize primitives (default True).

Properties

pure (bool) — spherical/cartesian type (read/write).
l (int) — angular momentum.
nprim (int) — number of primitives.
alpha / coeff — exponent and coefficient arrays.
origin — center coordinates.
ncart, nspher, nao — counts for cartesian/spherical functions and AOs.
cutoff — cutoff radius.

Methods

set_tol(tol) — set shell tolerance for cutoff computation.
scale_coeff(scale) — scale contraction coefficients.

Special behavior

len(shell) returns the number of primitives.
shell[i] returns the (alpha[i], coeff[i]) pair.

Example

s_shell = gxc.Shell(
    nprim=6, l=0, pure=True,
    alpha=[3047.5, 457.4, 103.9, 29.21, 9.286, 3.163],
    coeff=[0.00183, 0.01403, 0.06884, 0.2321, 0.4679, 0.3623],
    origin=[0.0, 0.0, 0.0]
)
print(s_shell.nao)  # 1 (s-shell has 1 AO)