add custom atomic scattering factors

classes_atoms.py
 - new classes defined, may not be used
 - code is incomplete

functions_crystallography.py
 - added new functions:
    - read_waaskirf_scattering_factor_coefs
    - scattering_factor_coefficients_neutron_ndb
    - scattering_factor_coefficients_neutron_sears
    - scattering_factor_coefficients_xray_itc
    - scattering_factor_coefficients_xray_waaskirf
    - scattering_factor_coefficients_electron_peng
    - scattering_factor_coefficients
    - analytical_scattering_factor
    - add_custom_form_factor_coefs
    - scattering_factor_coefficients_custom
    - xray_dispersion_table_custom
    - custom_scattering_factor
 - added custom form factor efficients and dispersion table
 - Added McPhase magnetic form factors
 - added load_magnetic_ff_coefs() and changed magnetic_form_factor() to use McPhase magnetic form factors
 - added hunds_rule(), glande() and atom_valence_state()
 - corrected xray_dispersion_corrections() to allow energy_kev=None

 functions_scattering.py
  - added custom scattering type

 classes_scattering.py
  - added custom scattering type in docs

 classes_plotting.py
  - fixed label issue

 functions_general.py
  - added liststr()

 examples
  - added example_custom_scattering_factors.py

 tests
  - added test_data_tables.py
  - all tests pass

Author: DanPorter

Dans_Diffraction/classes_atoms.py

@@ -175,7 +175,7 @@ def plot_distance(self, min_d=0.65, max_d=3.20, labels=None,
             axs[i].hist(dist[site]['dist'], range=ranges,
                         bins=int((ranges[1] - ranges[0]) / step))
             axs[i].set(ylabel='n. Atoms')
-        axs[-1].set(xlabel='$\AA$')
+        axs[-1].set(xlabel=r'$\AA$')
         if len(dist) > 1:
             for ax in axs.flat:
                 ax.label_outer()

Dans_Diffraction/classes_plotting.py

@@ -67,13 +67,13 @@ class Scattering:
         print(xtl.Scatter.print_all_refelctions()) # Returns formated string of all allowed reflections
         
         Allowed radiation types:
-            'xray','neutron','xray magnetic','neutron magnetic','xray resonant'
+            'xray','neutron','xray magnetic','neutron magnetic','xray resonant', 'custom'
     """
 
     #------Options-------
     # Standard Options
     _hkl = None  # added so recalculation not required
-    _scattering_type = 'xray'  # 'xray','neutron','xray magnetic','neutron magnetic','xray resonant'
+    _scattering_type = 'xray'  # 'xray','neutron','xray magnetic','neutron magnetic','xray resonant', 'custom'
     _scattering_specular_direction = [0, 0, 1]  # reflection
     _scattering_parallel_direction = [0, 0, 1]  # transmission
     _scattering_theta_offset = 0.0
@@ -527,9 +527,9 @@ def structure_factor(self, hkl=None, scattering_type=None, int_hkl=None, **kwarg
         if nenergy == 1 and npsi == 1:
             sf = sf[:, 0, 0]  # shape(nref)
         elif nenergy == 1:
-            sf = sf[:, 0, :]  # shape(nref, nenergy)
+            sf = sf[:, 0, :]  # shape(nref, npsi)
         elif npsi == 1:
-            sf = sf[:, :, 0]  # shape(nref, npsi)
+            sf = sf[:, :, 0]  # shape(nref, nenergy)
         if 'save' in kwargs:
             np.save(kwargs['save'], sf, allow_pickle=True)
             print("Saved %d structure factors to '%s'" % (sf.size, kwargs['save']))