Hypersalts designed using hyperalkali and halogen

To the best of our knowledge, hypersalts created from a hyperalkali and halogen have not been previously studied. Figure 25 displays the neutral structure of two possible hypersalts C and D, with D’s corresponding binding energy, AEA, and AIE in Table 10. The optimized neutral structure of C is the exact same as hypersalt B.

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Figure 25. Optimized neutral structure of hypersalts C and D, showing the addition of fluorine 8 used to create the hypersalt.

Hypersalt D (Figure 25) presents a perfect planar octagon structure with bond distances of

1.711 Å and alternating bond angles of 127o

and 143o

. Its HOMO, LUMO, and NBO are presented in Figures 26 and 27.

HOMO-LUMO Gap 8.54 eV

170 Figure 27. NBO of neutral hypersalt D.

The HOMO of the neutral has electrons localized on the halogen atoms, but the LUMO has electrons localized around the lithium atoms. The HOMO-LUMO gap of D for the neutral is found as 8.54 eV, very close to the gap calculated for hypersalt B.

A previous study by Giri et al.56

used NBO of the neutral to show the ionic character of a salt. If the charges of the atoms (cations and halogens) are nearly the same then the salt shows strong ionic character. Similarly, to hypersalts A and B, the large total positive charge on hypersalt D on the metal atoms and the large total negative charge on the halogen atoms, 0.901 and -0.901, respectively, also demonstrates the strong ionic character of the hypersalt.

As completed with the previous hypersalts A and B, the AEA and binding energy D is explored and summarized in table 10. The stability of D is also compared to B (being the most

stable isomer) and results in a difference of about +38 kJ mol-1

showing that the stability is close

to that of B. In addition, Hypersalt D’s BE (equation 3) is 7.84 eV and its AEA is -0.15 ± 0.05 eV.

Because hypersalt C is the same as B, its binding energy using ionic building blocks is also 7.69 eV, which makes D 0.15 eV higher in energy and therefore slightly more stable than B. Compared

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to A’s BE of 5.45 eV, D is more stable by 2.39 eV, making D the most stable hypersalt in terms of ionic moieties. Using neutral building blocks, however, provides BEs for the three structures 7.73 eV for A, 8.03 eV for B/C’s, 7.52 eV for D. Hypersalt B/C is the most stable hypersalt when using neutral parts, but hypersalt D has the largest BE, when using ionic parts, making it the strongest ionic compound/hypersalt containing Li and F investigated nowadays.

Table 10. Binding energy, AEA, and AIE of hypersalt D.a

Binding Energy Ions (eV) Binding Energy Ions (kJ mol-1 ) Binding Energy Neutrals (eV) Binding Energy Neutrals (kJ mol-1 ) AEA (eV) AIE (eV) Relative Energy (kJ mol-1 ) D. Li4F4 7.84 756.4 7.52 725.5 -0.15 10.9 38.3 a

Binding energies are calculated using equation 5 in eV and kJ mol-1

6.4 Conclusions

This study explores the design of a superalkali, superhalogen, hyperalkali, and hyperhalogen, which in turn, are used to develop possible hypersalts. The investigation uses a multistep composite computational job that follows the same setup of the CBS-QB3 method, and uses B3LYP in combination with the CBSB7+ basis set for optimizations and calculations. AIE’s, AEA’s, HOMO-LUMO energy gaps, and NBO’s are calculated for each presented species. Results confirm that the constructed hyperalkalis Li4F3 result in even lower AIE’s (3.86 eV and 3.67 eV for hyperalkali A and B, respectively) than the starting superalkali. The study also confirms the

structures for the designed hyperhalogens Li3F4 with higher AEA (7.61 eV and 5.67 eV for

hyperhalogen A and B, respectively) than the superhalogen building block. Hyperhalogens A and B are used to create hypersalts, following the idea that hypersalts are built from an alkali metal

bound to a hyperhalogen. This yields two possible salts A and B with the formula Li4F4. A and B

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indicating strong salts. Hypersalts C and D are designed from a hyperalkali plus a halogen atom with the formula Li4F4. Hypersalt C is identical to B, but D results in a binding energy of 7.84 eV. Between the three hypersalts, the ring structures of hypersalts B and D resulted in larger binding energies than linear hypersalt A. B and D's binding energy exceeding that of A by 2.24 eV and 2.12 eV, respectively. This may be due the ring structure causing a more even distribution among electrons. These conclusions bring into light a new way to make possibly more effective hypersalts using ring structures rather than linear. Considering a supersalt is constructed using a superhalogen and superalkali, future investigations will also explore the attainability of adding a hyperalkali to a hyperhalogen to create a hypersalt, as well as a hyperhalogen joined to a superalkali and hyperalkali joined to a superhalogen.