# PoissonSolverMaxMultipole

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#### PoissonSolverMaxMultipole

Section Hamiltonian::Poisson
Type integer

Order of the multipolar expansion for boundary corrections.

The Poisson solvers multigrid, cg, and cg_corrected (and fft with PoissonFFTKernel = multipole_correction) do a multipolar expansion of the given charge density, such that $\rho = \rho_{multip.expansion}+\Delta \rho$. The Hartree potential due to the $\rho_{multip.expansion}$ is calculated analytically, while the Hartree potential due to $\Delta \rho$ is calculated with either a multigrid or cg solver. The order of the multipolar expansion is set by this variable.

Default is 4 for PoissonSolver = cg_corrected and multigrid, and 2 for fft with PoissonFFTKernel = multipole_correction.

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