Hydrogen bonding and molecular mobility in liquid water in external electromagnetic fields

Abstract

Nonequilibrium molecular dynamics simulations of water have been performed in the isothermal–isobaric ensemble in the presence of external electromagnetic fields of varying intensity in the microwave to far-infrared frequency range, using a rigid/polarizable and a flexible/nonpolarizable potential model, from 260 to 400 K. Significant alterations in molecular mobility and hydrogen bonding patterns were found vis-à-vis zero-field conditions. In addition, the influence of the isothermal–isobaric ensemble on these observations was gauged by means of comparison with pure Newtonian simulation findings in the presence of external fields, and the former results were in reasonable accord with the latter.

Carbon nanotube assisted water self-diffusion across lipid membranes in the absence and presence of electric fields

“…In this regard, it has been shown that self-diffusion of water molecules through a (5,5) CNT embedded in a lipid bilayer is significantly enhanced by static electric fields, in contrast to CNTs of larger diameter. The electric field intensity of 0.0065 V/Å is weak in comparison to previous molecular simulation studies employing static and timevarying fields [29,30] and is also weak relative to fields generated by charge distributions [5]. A significant decrease in the fluctuations in the number of water 13 (11) to compute these values was 0.26nm, the projected length for a given water molecule along the pore axis in the non-field single-file pores.. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 value is +1 for a water dipole aligned along the +z-axis, and -1 for a water molecule aligned along the -z-axis.…”

Molecular dynamics simulations for the prediction of the dielectric spectra of alcohols, glycols and monoethanolamine

“…Nevertheless, Rick, Stuart, and Berne [19] and later English and MacElroy [20,21] determined the dielectric spectrum of water via equilibrium molecular dynamics simulations using the relationship between dipole moment fluctuations and the frequency-dependent dielectric constant initially developed by Neumann and Steinhauser [22,23]. Non-equilibrium molecular dynamics simulations have also been performed in order to model the microwave heating of water [24][25][26], and the effects of an external electromagnetic field on the conductivity of molten sodium chloride [27], rutile TiO 2 [28], nanoconfined fluids [29] and binary dimethylimidazolium-based ionic liquid/water solutions [30][31][32][33]. Additionally, recent work has been carried out on dielectric spectroscopy of more complex systems such as protein solutions [34][35][36].…”

Electric-Field and Friction Effects on Carbon Nanotube-Assisted Water Self-Diffusion Across Lipid Membranes

“…In the case of static fields, however, the water flux appears somewhat higher than that of the zero-field case, owing possibly to a similar reduction in water-number fluctuations therein, as found in previous work for (5,5) CNTs 26,27 ; an overlapping of error bars vis-à-vis the zero-field case, however, renders any firm statistical conclusion elusive in this respect. The (RMS) field intensities of 0.0065 V/Å are weak compared to previous molecular simulation studies employing static or time-varying electric fields 39 and also weak relative to fields generated by charge distributions 14 , and are substantially more realistic with respect to experiment. When arrays of CNTs are employed in the simulations the interpretation on the transport properties of the fluid within the individual nanotubes must take cognisance of inter-tube interactions.…”

“…Non-equilibrium MD simulations were also carried out in the presence of alternating electric fields 39 along the same z-axis (i.e., along the axes of the nanotubes). In this case, the RMS intensity was set to 0.0065 V/Å, the same as that of the peak frequency for the static EF, but the field does change direction every period between the +z and -z axis, ipso facto 40,41 .…”