Ab initio Molecular Orbital Calculations of Reduced Partition Function Ratios of Hydrated Lithium Ions in Ion Exchange Systems

Abstract Molecular orbital (MO) calculations at the HF/6-31G(d) level were carried out for the aquolithium ions, Li+(H2O)n (n = 3, 4, 5, 6, 8, 10 and 12) and the aquolithium ions interacting with the methyl sulfonate ion (MeS-), Li+MeS-(H2O)n (n = 0, 3,4, 5, 6, 7, 8 and 10) which were, respectively, intended to be substitutes for lithium species in the solution and resin phases of ion exchange systems for lithium isotope separation. For each of the species considered, at least one optimized structure with no negative frequency was obtained, and the 7Li-to-6Li isotopic reduced partition function ratio (RPFR) was estimated for the optimized structure. The solvation number in the primary solvation sphere was four, both in the solution and resin phases; three waters and MeS" formed the primary solvation sphere in the res in phase. Additional water molecules moved off to the secondary solvation sphere. It was found that consideration on the primary solvation sphere alone was insufficient for estimations of reduced partition function ratios of aquolithium ions. Although the agreement between the experimentally obtained lithium isotope fractionation and the calculated results is not satisfactory, it is pointed out that the HF/6-31 G(d) level of the theory is usable for elucidation of lithium isotope effects in aqueous ion exchange systems.

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Molecular Orbital Estimation of Reduced Partition Function Ratios of Lithium Interacting with Aromatic Hydrocarbons with Condensed Benzene Rings

Zeitschrift für Naturforschung A ◽

10.1515/zna-2003-5-614 ◽

2003 ◽

Vol 58 (5-6) ◽

pp. 325-332 ◽

Cited By ~ 3

Author(s):

Takao Oi ◽

Satoshi Yanase

Keyword(s):

Partition Function ◽

Molecular Orbital ◽

Aromatic Hydrocarbons ◽

Lithium Atom ◽

Isotope Effects ◽

Molecular Orbital Calculations ◽

Lithium Isotope ◽

Graphene Layers ◽

Stage Separation ◽

Benzene Rings

Molecular orbital calculations at the B3LYP/6-311G(d) level were carried out to elucidate the lithium isotope effects accompanying chemical insertion of lithium from 1-methoxybutane solution containing lithium and naphthalene to graphite. The lithium atom between the graphene layers of graphite was modeled as lithium atoms in 1:1 complexes of lithium and simple aromatic hydrocarbons with condensed benzene rings. The 7Li-to-6Li isotopic reduced partition function ratio (RPFR) was found to be a decreasing function of the number of benzene rings adjacent to the benzene ring above which the lithium atom was located, and was “saturated” at 1.04570 at 25 °C. The most plausible lithium species in the 1-methoxybutane solution was a lithium atom interacting with a naphthalene molecule and solvated by a 1-methoxybutane molecule in the contact ion pair manner. Its RPFR value was 1.07126 at 25 °C. The two RPFR values gave a single-stage separation factor of 1.024 for the lithium isotopes, which agreed well with the experimental value of 1.023.

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Lithium Isotope Effect Accompanying Electrochemical Insertion of Lithium into Liquid Gallium

Zeitschrift für Naturforschung A ◽

10.1515/zna-2010-0511 ◽

2010 ◽

Vol 65 (5) ◽

pp. 461-467 ◽

Cited By ~ 5

Author(s):

Keita Zenzai ◽

Ayaka Yasui ◽

Satoshi Yanase ◽

Takao Oi

Keyword(s):

Isotope Effect ◽

Isotope Effects ◽

Isotope Separation ◽

Ethylene Carbonate ◽

Quantitative Agreement ◽

Liquid Gallium ◽

Molecular Orbital Calculations ◽

Lithium Isotope ◽

Mixed Solution ◽

Separation Factors

Lithium was electrochemically inserted from a 1 : 2 (v/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1M LiClO4 into liquid gallium to observe lithium isotope effects accompanying the insertion. It was observed that the lighter isotope 6Li was preferentially fractionated into liquid gallium with the single-stage lithium isotope separation factors S, ranging from 1.005 to 1.031 at 50 °C and 1.003 to 1.024 at 25 °C. The lithium isotope effects estimated by molecular orbital calculations at the B3LYP/6-311G(d) level of theory agreed qualitatively with those of the experiments, but the quantitative agreement of the two was not satisfactory

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D/H and 18O/16O Isotopic Reduced Partition Function Ratios ofWater Molecules around a Sodium Ion

Zeitschrift für Naturforschung A ◽

10.1515/zna-2011-3-415 ◽

2011 ◽

Vol 66 (3-4) ◽

pp. 242-246 ◽

Cited By ~ 1

Author(s):

Takao Oi ◽

Akiko Otsubo

Keyword(s):

Aqueous Solution ◽

Partition Function ◽

Molecular Orbital ◽

Bulk Water ◽

Sodium Ion ◽

Water Molecules ◽

Molecular Orbital Calculations ◽

Salt Effects ◽

Hydration Sphere ◽

Model Water

With the final goal set at theoretical elucidation of experimentally observed isotope salt effects, molecular orbital calculations were performed to estimate the D/H and 18O/16O isotopic reduced partition function ratios (RPFRs) of water molecules around a sodium ion. As model water molecules in the ith hydration sphere of the sodium ion in sodium ion-bearing aqueous solution, we considered water molecules in the ith hydration sphere that were surrounded by water molecules in the (i+1)th hydration sphere in clusters, Na+(H2O)n (n up to 100). The calculations indicated that the 18O/16O RPFR in the primary hydration sphere is slightly smaller than that of bulk water while the D/H RPFR is practically the same as that of bulk water, and that the influence of the existence of the sodium ion is limited to the primary hydration sphere.

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Temperature Dependence of Lithium Isotope Effects in Ion Exchange Electromigration

Zeitschrift für Naturforschung A ◽

10.1515/zna-1987-0709 ◽

1987 ◽

Vol 42 (7) ◽

pp. 709-712

Author(s):

Yasuhiko Fujii ◽

Morikazu Hosoe ◽

Okamoto Makoto

Keyword(s):

Ion Exchange ◽

Cation Exchange ◽

Isotope Effects ◽

Isotope Separation ◽

Ion Exchange Chromatography ◽

Exchange Chromatography ◽

Separation Coefficient ◽

Lithium Isotope ◽

Increasing Temperature ◽

Exchange Membrane

The isotope separation coefficient of lithium electromigration through a cation exchange membrane is determined at 6, 11, 20 and 40 °C . It is found that this coefficient increases with temperature while the slope of the isotope distribution in the band decreases with increasing temperature. These tendencies are opposite to those usually observed in ion exchange chromatography.

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Oxygen and Hydrogen Isotopic Preference in Hydration Spheres of Magnesium and Calcium Ions

Zeitschrift für Naturforschung A ◽

10.5560/zna.2012-0122 ◽

2013 ◽

Vol 68 (5) ◽

pp. 362-370 ◽

Cited By ~ 7

Author(s):

Takao Oi ◽

Kunihiko Sato ◽

Kazuki Umemoto

Keyword(s):

Partition Function ◽

Aqueous Solutions ◽

Molecular Orbital ◽

Oxygen Isotopes ◽

Calcium Ions ◽

Hydrogen Isotopes ◽

Bulk Water ◽

Water Molecules ◽

Molecular Orbital Calculations ◽

Hydration Sphere

Molecular orbital calculations were performed to estimate the 18O/16O and D/H isotopic reduced partition function ratios (rpfrs) of water molecules around magnesium and calcium ions. As model for water molecules in the ith hydration sphere of the cation in aqueous solutions containing that cation, we considered water molecules in the ith hydration sphere that were surrounded by water molecules in the (i+1)th hydration sphere in clusters, M2+(H2O)n (M = Mg or Ca; n up to 100). The calculations indicated that the decreasing order of the 18O preference over 16O in the primary hydration sphere is Mg2+ > Ca2+ > bulk water. That is, water molecules in the primary hydration spheres of the Mg2+ and Ca2+ ions are expected to be enriched in the heavier isotope of oxygen relative to water molecules in bulk, and the degree of the enrichment is larger for the Mg2+ ion than for the Ca2+ ion. No such preference was observed for hydrogen isotopes in any hydration sphere or for oxygen isotopes in the secondary and outer hydration spheres.

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