Calculations of the tunneling splittings in water dimer and trimer using diffusion Monte Carlo

Abstract

Rearrangements and tunneling splittings of protonated water trimerThe diffusion Monte Carlo ͑DMC͒ method is used to calculate rovibrational bound states of the water dimer and trimer. The rigid body form of DMC is employed, together with correlated sampling of energy differences between states of different symmetry. This allows calculation of the tunneling splittings in ͑H 2 O͒ 2 and ͑H 2 O͒ 3 . The results for ͑H 2 O͒ 2 are in quite good agreement with those obtained using a basis set method, and also agree well with experiment. In addition, we have made predictions for similar splittings in ͑D 2 O͒ 3 and several water dimer isotopomers. In all the calculations, we have used the potential energy surface due to Millot and Stone which is known to give quite good agreement with experiment for the tunneling splittings in ͑H 2 O͒ 2 .

The World of Non-Covalent Interactions: 2006

“…The water clusters all exhibit very significant tunnelling motions and the corresponding large-amplitude motions and passages through the associated transition states resemble complicated energy landscapes 64 . A concerted effort by several theoretical groups from ab initio calculations by Xantheas 65 to full six-dimensional calculations by Leforestier 66 , earlier work of Kim and Jordan 67 , and the use of the diffusion Monte Carlo method by Clary 68,69 has now left us with a clearer picture of what is happening in water clusters and how their dynamics relate to the structure and dynamics of liquid water. The first conclusion that may be drawn is that when you build up the clusters to a certain size, the first three-dimensional structure is the hexamer, all other clusters are planar (or, more precisely, pseudo-planar because some hydrogens point out of plane) as can be seen in Fig.…”

Water pair potential of near spectroscopic accuracy. II. Vibration–rotation–tunneling levels of the water dimer

“…Following a more approximate five-dimensional treatment by Althorpe and Clary 49,50 in 1994 and some rigid-body quantum Monte Carlo calculations 51 giving estimates of the tunneling splittings, Leforestier et al 33 were in 1997 the first to calculate nearly exactly the VRT levels of the water dimer from a six-dimensional potential. They implemented a split Wigner pseudospectral method.…”

Concerted hydrogen-bond breaking by quantum tunneling in the water hexamer prism

“…Quantum simulations (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) have identified rearrangements which involve free hydrogen flips that break no hydrogen bonds, and bifurcations that break one bond (2).…”

“…The cluster dynamics can be probed by high-resolution rovibrational spectroscopy (1)(2)(3)(4)(5)(6)(7)(8)(9) and interpreted by theoretical simulations (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). The nature of the interactions between the water molecules is the same in the clusters as in the bulk (many-body forces beyond the three-body term are relatively weak) (28), and hence the cluster spectra can be used to test universal models (25,(29)(30)(31)(32) of the water intermolecular potential energy surface, giving insight into hydrogen bonding in all phases of water.…”