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Relation (3.7) is the most convenient one to use to compute the reciprocal
lattice parameters or any quantity related to them. Let *a, b, c* and
be the direct lattice parameters. The doubly covariant
coefficients of the metric tensor are then:

(3.15) |

Its determinant, that is the square of the volume of the direct lattice unit cell is equal to:

(3.16) |

By inversing 3.15 we obtain the doubly contravariant of the metric tensor,
*g*^{ij}

(3.17) |

Using (3.17), we can easily obtain the following relations:

(3.18) |

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