Reference:
# ACCUMULATED TABLE OF BOND VALENCE PARAMETERS
# The parameters given in the main table are the values of Ro and
# B used in the equation:
#
# bond valence = exp((Ro-R)/B)
#
# where R is the bond length. All values are in Angstrom units.
# Where significantly different values have been reported in the
# literature, they are listed in decreasing order of reliability.
#
# Bond valence parameters for atoms whose oxidation state is
# given as 9 do not have an oxidation state
# specified in the original paper. They may apply to a
# particular, but unspecified, oxidation state or they may be
# intended to apply to all oxidation states.
#
# The ammonium ion is listed under the symbol NH.