Proton hopping is a crucial phenomenon in science and engineering, up to life sciences. Here we present the first ab initio molecular-dynamics study of liquid water under intense electric fields, whose detailed description at a microscopic level is difficult to achieve experimentally [1]. We observe that the hydrogen-bond length and the molecular orientation are significantly modified at low-to-moderate field intensities. Fields beyond a threshold of about 0.35 V/Å are able to dissociate molecules and sustain an ionic current via a series of correlated proton jumps. Upon applying even more intense fields (~1.0 V/Å), a 15%-20% fraction of molecules are instan taneously dissociated and the resulting ionic flow yields a conductance of about 7.8 Ω-1 cm-1, in good agreement w ith experimental values. This result paves the way to quantum-accurate microscopic studies of the effect of electric fields on aqueous solutions. [1] A. M. Saitta, F. Saija, P. V. Giaquinta, Phys. Rev. Lett. 108, 207801 (2012).
Dissociation and proton-hopping conduction in water under electric field
GIAQUINTA, Paolo Vittorio
2013-01-01
Abstract
Proton hopping is a crucial phenomenon in science and engineering, up to life sciences. Here we present the first ab initio molecular-dynamics study of liquid water under intense electric fields, whose detailed description at a microscopic level is difficult to achieve experimentally [1]. We observe that the hydrogen-bond length and the molecular orientation are significantly modified at low-to-moderate field intensities. Fields beyond a threshold of about 0.35 V/Å are able to dissociate molecules and sustain an ionic current via a series of correlated proton jumps. Upon applying even more intense fields (~1.0 V/Å), a 15%-20% fraction of molecules are instan taneously dissociated and the resulting ionic flow yields a conductance of about 7.8 Ω-1 cm-1, in good agreement w ith experimental values. This result paves the way to quantum-accurate microscopic studies of the effect of electric fields on aqueous solutions. [1] A. M. Saitta, F. Saija, P. V. Giaquinta, Phys. Rev. Lett. 108, 207801 (2012).Pubblicazioni consigliate
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