Predictions for water clusters from a first-principles two- and three-body force field

Abstract

A new rigid-monomer three-body potential has been developed for water by fitting it to more than 70 thousand trimer interaction energies computed ab initio using coupled-cluster methods and augmented triple-zeta-quality basis sets. This potential was used together with a modified form of a previously developed two-body potential and with a polarization model of four-and higher-body interactions to predict the energetics of the water trimer, hexamer, and 24-mer. Despite using the rigidmonomer approximation, these predictions agree better with flexible-monomer benchmarks than published results obtained with flexible-monomer force fields. An unexpected finding of our work is that simple polarization models predict four-body interactions to within a few percent, whereas for three-body interactions these models are known to have errors on the order of 50%. © 2014 AIP Publishing LLC. [http://dx

Modelling Water: A Lifetime Enigma

“…[79] Feeling that the order of 10 5 data points is inadequate to build an accurate full 21-dimensional flexible-monomer three-body PES, the authors reverted to a rigid monomer model, consisting of the pair potential CCpol2 and three-body potential CCpol3. [80] CCpol2 is essentially the same as CC-pol-8s, except that shortrange damping is included to improve the description at very small intermolecular distances as these regions may be sampled during condensed phase simulations. The CCpol3 model, fitted to 71456 CCSD(T) energies, gives improved polarization from the use of three atomic polarization centres, instead of one.…”

A canonical approach to forces in molecules

“…Figure 2 The generation of accurate intermolecular interactions potentials, and thus forces, of water is a theoretical and computational challenging problem. Recent works have produced accurate potentials for water dimer [17][18][19], water trimer [20,21], and many body water interactions [20][21][22] exploiting the limits of current theoretical methods computational capabilities. Figure 4 shows the radial force distribution of water dimer generated from H 2 + .…”

Nine questions on energy decomposition analysis

“…A very accurate force field developed in Ref. was fitted to CCSD(T) calculations for the water dimer and trimer. Predictions of properties of clusters from this force field agree very well with accurate ab initio data available for some clusters.…”

“…In Ref. , not only the form of the fitting function was designed based on the behavior of SAPT components, but also the long‐range asymptotics was computed ab initio using SAPT codes. In contrast, while damping and exchange‐repulsion functional forms are also consistent with SAPT, the parameters in these terms are just free parameters of the fit.…”