Structural and Vibrational Properties of Liquid Water from van der Waals Density Functionals

Abstract

We present results for the structural and vibrational properties of the water molecule, water dimer, and liquid water at the experimental equilibrium density, as obtained with several van der Waals density functionals. The functional form originally proposed by Dion et al. [ Phys. Rev. Lett. 2004 , 92 , 246401 ], with an appropriately chosen local exchange functional, yields a description of the liquid superior to that of the semilocal functional PBE. In particular, a specific choice of the local exchange functional (optB88) fitted to quantum chemistry calculations yields the best agreement with experimental results for pair correlation functions although it is slightly inferior to other van der Waals functionals in describing infrared spectra. When using optB88, liquid water displays a hydrogen-bonded network less tightly bound than when using the PBE approximation. The performance of optB88 is definitely inferior to that of the PBE0 hybrid functional for the isolated molecule but only moderately so for the liquid. However, the computational cost of optB88 is much less than that of hybrid functionals; therefore the use of optB88 appears to be a sensible alternative to calculations implying the evaluation of the Fock operator, in cases when simulations of large systems are required.

Dispersion Interactions and Vibrational Effects in Ice as a Function of Pressure: A First Principles Study

“…This result, together with the energy difference between ice XI and ice VIII computed with PBE and vdW-DF2 (0.178 and 0.029 eV, respectively), shows that PBE overestimates the stability of phases that are mostly hydrogen bonded, with respect to those where hydrogen bonding is weaker and dispersion forces play a more important role. These findings are consistent with those of a recent study of water [26].…”

“…PBE and vdW-DF2 results exhibit several differences in the low P phase. The stretching mode frequencies are higher in ice XI and I c when using vdW-DF2, consistent with results obtained for liquid water [26] and in better agreement with the peaks observed in the measured IR spectra [27], at 3150, 3220, and 3380 cm À1 . Differences between the phonon density of states of ice VIII obtained at the PBE and vdW-DF2 level of theory are instead minor.…”

CO2 Capture by Metal–Organic Frameworks with van der Waals Density Functionals

“…Harmonic frequencies are known to be very sensitive to the choice of basis set, 47 pseudopotential choice, and functional. 48 Therefore, such a correction should be considered with caution.…”

The quantum nature of the OH stretching mode in ice and water probed by neutron scattering experiments

“…Upon increasing the hydrogen bond (H-bond) strength, the effective proton potential softens and consequently the E K and the O-H stretching frequency decreases (i.e., the O-H stretching frequency red shifts as the H-bond strength increases). [20][21][22][24][25][26] The redshift of the intramolecular stretching frequency of ice vibrational spectra, as compared to water and supercooled water (SW) spectra, is generally interpreted as a fingerprint of stronger H-bonding in ice. [27][28][29][30] In a recent study, 31 however, the redshift of the intramolecular stretching frequency was also proposed as a descriptor that could be used to estimate the interplay between quantum effects arising from zero point motion, and the strength of H-bonds, for a variety of systems ranging from H 2 O clusters, and HF dimers to solid HF and squaric acid.…”