  Recent work has shown that the many-body expansion of the interaction energy
can effectively be used to develop analytical representations of global
potential energy surfaces (PESs) for water. In this study, the role of short-
and long-range contri- butions at different orders is investigated by analyzing
water potentials that treat the leading terms of the many-body expansion
through implicit (i.e., TTM3-F and TTM4-F PESs) and explicit (i.e., WHBB and
MB-pol PESs) representations. It is found that explicit short-range
representations of 2-body and 3-body interactions along with a physically
correct integration of short- and long-range contributions are necessary for an
accurate representation of the water interactions from the gas to the condensed
phase. Similarly, a complete many-body representation of the dipole moment
surface is found to be crucial to reproducing the correct intensities of the
infrared spectrum of liquid water.
