Molecular Dynamics Simulation of Tri-<i>n</i>-butyl-Phosphate Liquid: A Force Field Comparative Study

Cui, Shaogang; Almeida, Valmor F. de; Hay, Benjamin P.; Ye, Xianggui; Khomami, Bamin

doi:10.1021/jp207089e

Cited by 42 publications

(85 citation statements)

References 31 publications

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“…It is found the TBP electric dipole moment has a significant effect on the predicted water solubility. By scaling down the original DFT-based atomic partial charges of the TBP molecular model by 0.9, 15 water solubility close to that measured in experiments was predicted.…”

Section: Discussionmentioning

confidence: 60%

“…We attribute this significant over-prediction to the relatively large dipole moment of the TBP force field. In our previous study 15 we have established that these TBP models exhibit larger dipole moment than the experimentally measured value, 3.07-3.32 D.…”

Section: Molecular Dynamics Simulation Detailsmentioning

confidence: 67%

“…For water, we used a flexible SPC model. 17 For TBP, we used a recently developed OPLS-DFT model 15 and compared to the Amber-MNDO model. 15 For n-dodecane, we used a re-optimized OPLS All-Atom force field with scaling factor at 0.4.…”

Section: Molecular Modelsmentioning

confidence: 99%

“…17 For TBP, we used a recently developed OPLS-DFT model 15 and compared to the Amber-MNDO model. 15 For n-dodecane, we used a re-optimized OPLS All-Atom force field with scaling factor at 0.4. 18 The parameters for cross interactions between different molecular species (atomic groups) were derived using the standard Lorentz-Berthelot rules.…”

Section: Molecular Modelsmentioning

confidence: 99%

“…In a prior study, we have examined several TBP force field models. 15 However, the performance of these TBP force fields in modeling water extraction remains to be tested. Therefore, in this study, we investigate the performance of selected TBP force fields on water extraction to derive fundamental molecular level complexation mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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Quantify Water Extraction by TBP/Dodecane via Molecular Dynamics Simulations

Khomami

Cui

Almeida

et al. 2013

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Objective: The purpose of this project is to quantify the interfacial transport of water into the most prevalent nuclear reprocessing solvent extractant mixture, namely tri-butylphosphate (TBP) and dodecane, via massively parallel molecular dynamics simulations on the most powerful machines available for open research. Specifically, we will accomplish this objective by evolving the water/TBP/dodecane system up to 1 ms elapsed time, and validate the simulation results by direct comparison with experimentally measured water solubility in the organic phase. The significance of this effort is to demonstrate for the first time that the combination of emerging simulation tools and state-of-the-art supercomputers can provide quantitative information on par to experimental measurements for solvent extraction systems of relevance to the nuclear fuel cycle.Efforts and Results: To achieve the object described above, initially, the single component, single phase systems were studied to verify existing and develop new molecular models, followed by a single phase mixture, and then finally the complete twophase water extraction system. Specifically, the systems we studied are: (1) pure TB; (2) n-doedecane; (3) TBP/n-dodecane mixture; and (4) the complete extraction system: water-TBP/n-dodecane two phase system to gain deep insight into the water extraction process. We have completely achieved our goal of extracting water molecules into the TBP/n-dodecane mixture to saturation and obtained favorable comparison with experiment. Many insights into fundamental molecular level processes and physics were obtained from the process. Most importantly, we found that the dipole moment of the 2 Bu=C 4 extracting agent is crucially important in affecting the interface roughness and the extraction rate of water molecules into the organic phase. In addition, we have identified shortcomings in the existing OPLS-AA force field potential for long-chain alkanes. The significance of this force field is that it is supposed to be optimized for molecular liquid simulations. We found that it failed for n-dodecane and/or longer chains to correctly predict the liquid state and thus not usable for our water extraction simulation. We have proposed a simple modification to circumvent the artificial crystallization of the long alkane chains applicable at ambient condition.(b) Effort performed and the accomplishments achieved TBP Force Field Model DevelopmentWe conducted force field survey on 4 sets of force field parameters for TBP, a molecule composed of a phosphate head group and three butyl tails as shown in Figure 1. The 4 sets of parameters are based on adoption of Van der Waals parameters for the phosphoryl head group and the butyl tail group of the TBP molecules, from separate force field models already in use. In particular, we used the Amber parameters for the Van der Waals interaction of the phosphoryl group, combined with either the Amber or the OPLS-AA (Optimized Potential for Liiquid Simulation-All Atoms) force field for the butyl tail...

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Section: Discussionmentioning

confidence: 60%

Section: Molecular Dynamics Simulation Detailsmentioning

confidence: 67%

Section: Molecular Modelsmentioning

confidence: 99%

Section: Molecular Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantify Water Extraction by TBP/Dodecane via Molecular Dynamics Simulations

Khomami

Cui

Almeida

et al. 2013

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Spectroscopic and structural characterization of pure and FeCl3-containing tri-n-butyl phosphate

Calandra

Caschera

et al. 2014

Colloid Polym Sci

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The spectroscopic properties and liquid structure of pure tri-n-butyl phosphate (TBP) and FeCl 3 /TBP solutions have been investigated by Uv-Vis and Raman spectroscopies, X-ray diffraction and conductometry. Uv-Vis and Raman spectra, supported by conductometric measurements, consistently indicate that the solubilized salt is present mostly as TBP n [FeCl 3−n ] n+ and FeCl 4 − complex ions due to specific interaction with the TBP phosphate group. Thanks to this interaction, a high amount of salt (up to 13 % w/w) can be dissolved despite the relatively low dielectric constant of TBP. The X-ray diffractogram of pure TBP has been interpreted in terms of three main contributions which can be attributed to spatial pair correlations between atoms of interacting TBP molecules. In the presence of increasing FeCl 3 amounts, it has been observed a progressive structuring effect, exerted by the dissolved salt, on the layers of opportunely oriented TBP molecules due to the formation of the complex ionic species. By simple treatment with NaBH 4 , the synthesis of Fe nanoparticles has been achieved. The absence of water, the easiness of preparation, the high amount of salt which can be suspended and the peculiar physico-chemical properties of such systems are all elements worth of note for the fields of nanoparticle synthesis and for specialized technological applications.

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