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## 4.2 Memory requirements

A typical self-consistency or molecular-dynamics run requires a maximum memory in the order of O double precision complex numbers, where

O = mMN + PN + pN1N2N3 + qNr1Nr2Nr3

with m, p, q = small factors; all other variables have the same meaning as above. Note that if the Γ -point only (k = 0) is used to sample the Brillouin Zone, the value of N will be cut into half.

For hybrid DFTs, additional storage of Ox double precision complex numbers is needed (for Fourier-transformed Kohn-Sham states), with Ox = xNqMN1N2N3 and x = 0.5 for Γ -only calculations, x = 1 otherwise.

The memory required by the phonon code follows the same patterns, with somewhat larger factors m, p, q.