More informative error for expanded cutoff
@@ -834,8 +834,10 @@ class AlchemicalPhase(object):
elif (thermodynamic_state.pressure is not None and
min_box_dimension * fluctuation_size < 2.0 * expanded_cutoff_distance):
raise RuntimeError('Barostated box sides must be at least {} Angstroms '
- 'to correct for missing dispersion interactions'
- ''.format(expanded_cutoff_distance/unit.angstrom * 2))
+ 'to correct for missing dispersion interactions. The '
+ 'minimum dimension of the provided box is {} Angstroms'
+ ''.format(expanded_cutoff_distance/unit.angstrom * 2,
+ min_box_dimension/unit.angstrom))
logger.debug('Setting cutoff for fully interacting system to {}. The minimum box '
'dimension is {}.'.format(expanded_cutoff_distance, min_box_dimension))
