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LSPECTRAL

If LSPECTRAL = .TRUE. is set, the imaginary part of the independent particle polarizability ${\displaystyle \chi _{\mathbf {q} }^{0}({\mathbf {G} },{\mathbf {G} }',\omega )}$ is calculated first, and afterwards the full independent particle polarizability is determined using a Kramers-Kronig (or Hilbert) transform. This reduces the computational work load by almost a factor NOMEGA/2. The downside of the coin is that the response function must be kept in memory for all considered frequencies, which can cause excessive memory requirements. VASP therefore distributes the dielectric functions among the available compute nodes.