LMAX

LMAX defines the maximum angular momentum number to be used in the spherical harmonics expansion, used for calculating the scattering matrices within each layer. In general, this is determined by the PHASESHIFT_EPS parameter, based on the maximum phase-shift values at a given energy. The LMAX parameter can be used to instead fix it to a constant value for all energies, or to define upper and lower bounds.

Default: Determined by PHASESHIFT_EPS, minimum 6

Syntax:

LMAX = 9     ! Use a constant LMAX=9 at all energies
LMAX = 6-11  ! Base LMAX on PHASESHIFT_EPS, but keep between bounds 6 and 11. Equivalent: '6:11' or '6 11'

Acceptable values: one or two integer values between 1 and 18

Energy-dependent LMAX values are used in the reference calculation (TensErLEED version 1.61 and higher). Delta calculations will use the highest LMAX, filling missing matrix elements (from Tensors with lower LMAX) with zeroes.

Because the PHASESHIFT_EPS uses a relatively low cutoff (“fine”) by default, most calculations can be accelerated by setting an upper bound for LMAX.