def rotational_symmetry_number(gra, key1, key2, lin_keys=None):
""" get the rotational symmetry number along a given rotational axis
:param gra: the graph
:param key1: the first atom key
:param key2: the second atom key
"""
ngb_keys_dct = atoms_neighbor_atom_keys(without_dummy_atoms(gra))
imp_hyd_vlc_dct = atom_implicit_hydrogen_valences(implicit(gra))
axis_keys = {key1, key2}
# If the keys are part of a linear chain, use the ends of that for the
# symmetry number calculation
lin_keys_lst = linear_segments_atom_keys(gra, lin_keys=lin_keys)
for keys in lin_keys_lst:
if key1 in keys or key2 in keys:
if len(keys) == 1:
key1, key2 = sorted(ngb_keys_dct[keys[0]])
else:
key1, = ngb_keys_dct[keys[0]] - {keys[1]}
key2, = ngb_keys_dct[keys[-1]] - {keys[-2]}
axis_keys |= set(keys)
break
sym_num = 1
for key in (key1, key2):
if key in imp_hyd_vlc_dct:
ngb_keys = ngb_keys_dct[key] - axis_keys
if len(ngb_keys) == imp_hyd_vlc_dct[key] == 3:
sym_num = 3
break
return sym_num
def bond_symmetry_numbers(gra, frm_bnd_key=None, brk_bnd_key=None):
""" symmetry numbers, by bond
the (approximate) symmetry number of the torsional potential for this bond,
based on the hydrogen counts for each atom
It is reduced to 1 if one of the H atoms in the torsional bond is a
neighbor to the special bonding atom (the atom that is being transferred)
"""
imp_gra = implicit(gra)
atm_imp_hyd_vlc_dct = atom_implicit_hydrogen_valences(imp_gra)
bnd_keys = bond_keys(imp_gra)
tfr_atm = None
if frm_bnd_key and brk_bnd_key:
for atm_f in list(frm_bnd_key):
for atm_b in list(brk_bnd_key):
if atm_f == atm_b:
tfr_atm = atm_f
if tfr_atm:
neighbor_dct = atoms_neighbor_atom_keys(gra)
nei_tfr = neighbor_dct[tfr_atm]
atms = gra[0]
all_hyds = []
for atm in atms:
if atms[atm][0] == 'H':
all_hyds.append(atm)
else:
nei_tfr = {}
bnd_symb_num_dct = {}
bnd_symb_nums = []
for bnd_key in bnd_keys:
bnd_sym = 1
vlc = max(map(atm_imp_hyd_vlc_dct.__getitem__, bnd_key))
if vlc == 3:
bnd_sym = 3
if tfr_atm:
for atm in nei_tfr:
nei_s = neighbor_dct[atm]
h_nei = 0
for nei in nei_s:
if nei in all_hyds:
h_nei += 1
if h_nei == 3:
bnd_sym = 1
bnd_symb_nums.append(bnd_sym)
bnd_symb_num_dct = dict(zip(bnd_keys, bnd_symb_nums))
# fill in the rest of the bonds for completeness
bnd_symb_num_dct = dict_.by_key(bnd_symb_num_dct,
bond_keys(gra),
fill_val=1)
return bnd_symb_num_dct
def atom_count(gra, dummy=False, with_implicit=True):
""" count the number of atoms in this molecule
by default, this includes implicit hydrogens and excludes dummy atoms
"""
if not dummy:
gra = without_dummy_atoms(gra)
natms = len(atoms(gra))
if with_implicit:
atm_imp_hyd_vlc_dct = atom_implicit_hydrogen_valences(gra)
natms += sum(atm_imp_hyd_vlc_dct.values())
return natms
def from_graph(gra):
""" networkx graph object from a molecular graph
"""
nxg = networkx.Graph()
nxg.add_nodes_from(atom_keys(gra))
nxg.add_edges_from(bond_keys(gra))
networkx.set_node_attributes(nxg, atom_symbols(gra), 'symbol')
networkx.set_node_attributes(nxg, atom_implicit_hydrogen_valences(gra),
'implicit_hydrogen_valence')
networkx.set_node_attributes(nxg, atom_stereo_parities(gra),
'stereo_parity')
networkx.set_edge_attributes(nxg, bond_orders(gra), 'order')
networkx.set_edge_attributes(nxg, bond_stereo_parities(gra),
'stereo_parity')
return nxg
def terminal_heavy_atom_keys(gra):
""" terminal heavy atoms, sorted by atom type and hydrogen count
"""
gra = implicit(gra)
atm_imp_hyd_vlc_dct = atom_implicit_hydrogen_valences(gra)
atm_keys = [
key for key, ngb_keys in atoms_neighbor_atom_keys(gra).items()
if len(ngb_keys) == 1
]
atm_keys = sorted(atm_keys,
key=atm_imp_hyd_vlc_dct.__getitem__,
reverse=True)
atm_symbs = dict_.values_by_key(atom_symbols(gra), atm_keys)
srt = automol.formula.argsort_symbols(atm_symbs, symbs_first=('C', ))
atm_keys = tuple(map(atm_keys.__getitem__, srt))
return atm_keys