# qml.qchem.mol_density_matrix¶

mol_density_matrix(n_electron, c)[source]

Compute the molecular density matrix.

The density matrix $$P$$ is computed from the molecular orbital coefficients $$C$$ as

$P_{\mu \nu} = \sum_{i=1}^{N} C_{\mu i} C_{\nu i},$

where $$N = N_{electrons} / 2$$ is the number of occupied orbitals. Note that the total density matrix is the sum of the $$\alpha$$ and $$\beta$$ density matrices, $$P = P^{\alpha} + P^{\beta}$$.

Parameters
• n_electron (integer) – number of electrons

• c (array[array[float]]) – molecular orbital coefficients

Returns

density matrix

Return type

array[array[float]]

Example

>>> c = np.array([[-0.54828771,  1.21848441], [-0.54828771, -1.21848441]])
>>> n_electron = 2
>>> mol_density_matrix(n_electron, c)
array([[0.30061941, 0.30061941], [0.30061941, 0.30061941]])


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