Molecular Association in Alkali Halide Vapors

Datz, S.; Smith, Walter T.; Taylor, Ellison H.

doi:10.1063/1.1700983

“…(BK) to 129 cm −1 (12-6 LJ) compared to the reference force fields with RMSDs from 121 cm −1 (JC) to 316 cm −1 (pol-CHARMM). As mentioned earlier, in alkali halide vapours an appreciable amount of dimers and trimers exists in addition to monomers.The fraction of such dimers and trimers is largest for lithium and fluoride salts and decreases towards caesium and iodide salts,87 and complicates the measurements for the lighter alkali halides, leading to larger experimental errors 92. One possible explanation for the systematic overestimation of the vibrational frequencies of the lighter alkali halides with all force fields The dipole moment increases from lithium to caesium salts, and in each alkali halide series from fluoride to iodide, and is directly proportional to the interionic distance.…”

mentioning

confidence: 99%

Phase-Transferable Force Field for Alkali Halides

Walz

¹

,

Ghahremanpour

²

,

Maaren

³

et al. 2018

J. Chem. Theory Comput.

View full text Add to dashboard Cite

A longstanding goal of computational chemistry is to predict the state of materials in all phases with a single model. This is particularly relevant for materials that are difficult or dangerous to handle or compounds that have not yet been created. Progress towards this goal has been limited as most work has concentrated on just one phase, often determined by particular applications. In the framework of the development of the Alexandria force field we present here new polarizable force fields for alkali halides with Gaussian charge distributions for molecular dynamics simulations. We explore different descriptions of the Van der Waals interaction, like the commonly applied 12-6 Lennard-Jones (LJ), and compare it to \softer" ones, such as 8-6 LJ, Buckingham and a modified Buckingham potential. Our results for physico-chemical properties of the gas, liquid and solid phase of alkali halides, are compared to experimental data and calculations with reference polarizable and non-polarizable force fields. The new polarizable force field that employs a modified Buckingham potential predicts the tested properties for gas, liquid and solid phases with a very good accuracy. In contrast to reference force fields, this model reproduces the correct crystal structures for all alkali halides at low and high temperature. Seeing that experiments with molten salts may be tedious due to high temperatures and their corrosive nature, the models presented here can contribute significantly to our understanding of alkali halides in general and melts in particular. File list (2) download file view on ChemRxiv walz2018a-phase-transferable-FF-alkali-halides.pdf (2.05 MiB) download file view on ChemRxiv walz2018a-phase-transferable-FF-alkali-halides-support...

show abstract

“…However, as the concentrations of Al 3+ in the mantle are too low to meet this entire need, iron in the olivine disproportionates, with Fe 3+ deputizing for the lacking Al 3+ , while the native iron Fe 0 tends to gravitate to the core [ 61 , 62 , 63 , 85 ]. The result is a relatively oxidized volatisphere comprising CO 2 > H 2 O >> N 2 [ 85 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 ].…”

Section: The “Pond” In the Hellish Hadeanmentioning

confidence: 99%

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Russell

¹

2021

Life

View full text Add to dashboard Cite

The assumption that there was a “water problem” at the emergence of life—that the Hadean Ocean was simply too wet and salty for life to have emerged in it—is here subjected to geological and experimental “reality checks”. The “warm little pond” that would take the place of the submarine alkaline vent theory (AVT), as recently extolled in the journal Nature, flies in the face of decades of geological, microbiological and evolutionary research and reasoning. To the present author, the evidence refuting the warm little pond scheme is overwhelming given the facts that (i) the early Earth was a water world, (ii) its all-enveloping ocean was never less than 4 km deep, (iii) there were no figurative “Icelands” or “Hawaiis”, nor even an “Ontong Java” then because (iv) the solidifying magma ocean beneath was still too mushy to support such salient loadings on the oceanic crust. In place of the supposed warm little pond, we offer a well-protected mineral mound precipitated at a submarine alkaline vent as life’s womb: in place of lipid membranes, we suggest peptides; we replace poisonous cyanide with ammonium and hydrazine; instead of deleterious radiation we have the appropriate life-giving redox and pH disequilibria; and in place of messy chemistry we offer the potential for life’s emergence from the simplest of geochemically available molecules and ions focused at a submarine alkaline vent in the Hadean—specifically within the nano-confined flexible and redox active interlayer walls of the mixed-valent double layer oxyhydroxide mineral, fougerite/green rust comprising much of that mound.

show abstract

“…Depending on temperature and pressure, a significant fraction of the vaporised salt can exist as dimers (AH) 2 , and for NaF, LiCl and LiBr even trimers (AH) 3 have been observed. 87,88 In the parameterisation, physical properties from monomers were used, and here we report simulation results for this species.…”

Section: Gas Phasementioning

confidence: 99%

“…The fraction of such dimers and trimers is largest for lithium and fluoride salts and decreases towards caesium and iodide salts, 87 and complicates the measurements for the lighter alkali halides, leading to larger experimental errors. 92 One possible explanation for the systematic overestimation of the vibrational frequencies of the lighter alkali halides with all force fields could be partially due to this larger experimental error.…”

Section: Dissociation Energymentioning

confidence: 99%

Phase-Transferable Force Field for Alkali Halides

Walz¹,

Ghahremanpour²,

Maaren³

et al. 2018

Preprint

View full text Add to dashboard Cite

A longstanding goal of computational chemistry is to predict the state of materials in all phases with a single model. This is particularly relevant for materials that are difficult or dangerous to handle or compounds that have not yet been created. Progress towards this goal has been limited as most work has concentrated on just one phase, often determined by particular applications. In the framework of the development of the Alexandria force field we present here new polarizable force fields for alkali halides with Gaussian charge distributions for molecular dynamics simulations. We explore different descriptions of the Van der Waals interaction, like the commonly applied 12-6 Lennard-Jones (LJ), and compare it to \softer" ones, such as 8-6 LJ, Buckingham and a modified Buckingham potential. Our results for physico-chemical properties of the gas, liquid and solid phase of alkali halides, are compared to experimental data and calculations with reference polarizable and non-polarizable force fields. The new polarizable force field that employs a modified Buckingham potential predicts the tested properties for gas, liquid and solid phases with a very good accuracy. In contrast to reference force fields, this model reproduces the correct crystal structures for all alkali halides at low and high temperature. Seeing that experiments with molten salts may be tedious due to high temperatures and their corrosive nature, the models presented here can contribute significantly to our understanding of alkali halides in general and melts in particular.<br>

show abstract

Molecular Association in Alkali Halide Vapors

Cited by 47 publications

References 20 publications

Phase-Transferable Force Field for Alkali Halides

Phase-Transferable Force Field for Alkali Halides

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Phase-Transferable Force Field for Alkali Halides

Contact Info

Product

Resources

About