This keyword sets the number of radial (\(n_\mathrm{max}^\mathrm{R}\)) and angular (\(n_\mathrm{max}^\mathrm{A}\)) descriptor components as introduced in Sect. II.B and Eq. (2) of [Fan2022b]. The syntax is:

n_max <n_max_R> <n_max_A>

where n_max_R and n_max_A are \(n_\mathrm{max}^\mathrm{R}\) and \(n_\mathrm{max}^\mathrm{A}\), respectively. The two parameters must satisfy \(0 \leq n_\mathrm{max}^\mathrm{R},n_\mathrm{max}^\mathrm{A} \leq 19\).

The default values of \(n_\mathrm{max}^\mathrm{R}=4\) and \(n_\mathrm{max}^\mathrm{A}=4\) are relatively small but typically yield high speed.

Note: These parameters should not be confused with \(N_\mathrm{bas}^\mathrm{R}\) and \(N_\mathrm{bas}^\mathrm{A}\), which are set via the basis_size keyword.