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Structure and harmonic frequencies of water molecule and dimer by Quantum Monte Carlo

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The correct description of water-water interactions is still a challenge for many electronic structure methods, such as density functional theory. the Quantum Monte Carlo methods have proven to describe  correctly both the dipole moment and the binding energy of the water dimer1 the latter being crucial for a proper description of the Hydrogen bond.


Figure 1 : The component  along the x axis of the forces acting on the oxygen atom of the water monomer as a function of the atomic movement ?R of the oxygen


As variational wave function we used an Antisymmetrized Geminal power with a Jastrow factor (JAGP), fully optimized through a stochastic reconfiguration procedure (SRH)2. Within this scheme we obtained Variational Monte Carlo (VMC) results, which are of the same quality than those obtained by the Diffusion Monte Carlo (LRDMC)2 a much more computationally demanding scheme. In the present contribution we have used the extended AGP molecular orbitals scheme described in reference3 to study the electronic and structural properties of the water monomer and dimer. Ionic forces are calculated at the VMC level using the scheme introduced in reference4. Normal modes and harmonic frequencies are calculated for the water monomer and compared with the experimental data and quantum chemistry calculation such as Coupled Cluster5,6.


1 F. Sterpone et al., J. Chem. Theo. Comp., 4, 1428-1434 (2008)

2 S. Sorella, Phys. Rev. B 64, 024512 (2001)

3M. Marchi et al., J. Chem. Phys. 131, 154116 (2009)

4C. Attaccalite and S. Sorella, Phys. Rev. Lett. 100, 114501 (2008)

5D. Feller, A. Peterson, J. Chem. Phys. 131, 154306 (2009)

6P.H.-L. Sit,, N. Marzari, J. Chem. Phys. 122, 204510 (2005)

7C. Filippi and C. J. Umrigar, Phys. Rev. B, 61R, 16291 (2000)


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