from msspec.calculator import MSSPEC
from ase  import Atoms
import numpy as np

symbol = 'Ni'            # The kind of atom for the chain
a = 3.499 * np.sqrt(2)/2 # The distance bewteen 2 atoms
                         # in [101] direction

chain = Atoms(symbol*2, positions=[(0,0,0), (0,0,a)])
chain.rotate(45, 'y')

calc = MSSPEC(spectroscopy='PED', algorithm='expansion')
calc.calculation_parameters.scattering_order = 1

chain.emitter = 0
calc.set_atoms(chain)

data = calc.get_theta_scan(level='3s', theta=np.arange(0,80,0.5))
data.view()