Density-functional-based molecular-dynamics simulations of molten salts

Abstract

The physicochemical properties of two molten salts, namely, KCl and NaCl, have been studied with a molecular-dynamics approach using a density-functional-based tight-binding (DFTB) model. The obtained results have been compared with a number of previously reported simulations, carried out on smaller systems and using classical force-field techniques. A good agreement has been found for both structural parameters and macroscopic properties, such as self-diffusion coefficients. Furthermore, our DFTB results are very close to the available experimental data. From a more general point of view, our results demonstrate the applicability of DFTB as an efficient tool in the modeling of melts. At the same time, the quality of the obtained results supports the use of this as a reliable alternative to the more expensive ab initio dynamics approaches, if accurate parameters are provided.

Spotlight on ionic liquids

“…Structures of molten salts have been widely investigated both experimentally using scattering methods, [12][13][14] as well as using classical [15][16][17][18][19] and quantum methods molecular dynamics ͑MD͒ simulations. 20,21 The popularity of ILs as a research topic is reflected in the numerous reviews, 1,10,22 monographs, 6 and conference proceedings [23][24][25] that have been published recently. The reviews by Hamaguchi and Ozawa 26 and Kobrak, 27 as well as several journal special issues [28][29][30] have focused primarily on the physical chemistry and chemical physics of ILs.…”

Modeling Solute Thermokinetics in LiCI-KCI Molten Salt for Nuclear Waste Separation

“…Statistical convergence errors on FPMD volumes are typically less than 0.1 Å 3 /atom (less than 0.5 %). Previous simulations with IPMD and DFT-TB fixed the volume to experimental values [88,89,98,99]. The Tosi-Fumi potentials used in IPMD simulations [88,89] overestimate the experimental volume by 6-7 % (Figure 4.1(a)) corresponding to a pressure of 0.31 GPa in the simulations [88].…”

“…Experimental and IPMD computational data exists in the literature for comparison in both LiCl [88,116,122,123] and KCl [88,89,98,123,124], but only IPMD computational data exists for self-diffusion in eutectic LiCl-KCl [88,89].…”

“…The NaCl and KCl molten salt systems were studied with density-functional-based tight-binding methods (DFT-TB) [98]. While DFT-TB methods are similar to FPMD, they are not fully self-consistent.…”

“…While DFT-TB methods are similar to FPMD, they are not fully self-consistent. Furthermore, volumes within the work of Hazebroucq, et al [98] were fixed to experimental values rather than predicted. FPMD simulations were conducted in the liquid Flibe (Li 2 BeF 4 ) using the Car-Parrinello method [99], but the focus was primarily on diffusion, again at a fixed experimental volume.…”