Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

The storage of electric energy is of ever growing importance for our modern, technology-based society, and novel battery systems are in the focus of research. The substitution of conventional metals as redox-active material by organic materials offers a promising alternative for the next generation of rechargeable batteries since these organic batteries are excelling in charging speed and cycling stability. This review provides a comprehensive overview of these systems and discusses the numerous classes of organic, polymer-based active materials as well as auxiliary components of the battery, like additives or electrolytes. Moreover, a definition of important cell characteristics and an introduction to selected characterization techniques is provided, completed by the discussion of potential socio-economic impacts.

Polymer-Based Organic Batteries

A Calculation of Atomic Structures. By D. R. Hartree Pp. xiii, 181. 40s. 1957. (Wiley, New York)

The review focuses on various hydrogen producing and storing methods that can be employed for creating a hydrogen economy. The latest advancements that have been made on different hydrogen storing materials and hydrogen storing technologies which have proven useful both on gravimetric and volumetric basis, have been highlighted. The encouraging and hopeful aspect of their developments is that the most of the materials are approaching the hydrogen storing capacity requirement that have been laid down by DOE. The classification of different systems has been done on basis of their storage mechanism, keeping in mind their advantages and disadvantages while they tend to store hydrogen both in the atomic and molecular form.

Hydrogen storage: Materials, methods and perspectives

6.1. Molecular Vibrations PR58 6.2. Molecular Internal Rotations PR58 6.3. Chemical Reactions PR58 7. Dynamical Variants PR62 7.1. Quantum Fluid Density Functional Theory PR62 7.2. Atom-Field Interactions PR62 7.3. Ion-Atom Collisions PR62 7.4. Chemical Kinetics PR62 8. Spin Dependent Generalizations PR63 8.1. {N, Ns, v(r b)} Representation PR63 8.2. {NR, N , v(r b)} Representation PR64 9. Conclusions PR65 10. Abbreviations and Symbols of Some Important Subjects/Quantities PR

Update 2 of: Electrophilicity Index

In this article, we analyze the stability, reactivity, and possible aromatic behavior of two recently reported clusters (Reveles, J. U.; Khanna, S. N.; Roach, P. J.; Castleman, A. W., Jr. Proc. Natl. Acad. Sci. 2006, 103, 18405), viz., Al(7)C(-) and Al(7)O(-) in the light of the principles of the maximum hardness and minimum electrophilicity as well as the nucleus-independent chemical shift values. Stability of these clusters in the context of addition/removal of an electron or an Al atom is now clearly understood.

Stability, reactivity, and aromaticity of compounds of a multivalent superatom.

Conceptual density functional theory provides a method for analyzing the chemical reactivity in terms of different global reactivity descriptors including electrophilicity and their local counterparts like philicity. These concepts’ definitions and various applications that demonstrate their interpretive power are discussed. Global and local electrophilicities are able to account for a wide variety of chemical phenomena.

Electrophilicity index within a conceptual DFT framework

Most electrolytes currently used in Li-ion batteries contain halogens, which are toxic. In the search for halogen-free electrolytes, we studied the electronic structure of the current electrolytes using first-principles theory. The results showed that all current electrolytes are based on superhalogens, i.e., the vertical electron detachment energies of the moieties that make up the negative ions are larger than those of any halogen atom. Realizing that several superhalogens exist that do not contain a single halogen atom, we studied their potential as effective electrolytes by calculating not only the energy needed to remove a Li+ ion but also their affinity towards H2O. Several halogen-free electrolytes are identified among which Li(CB11H12) is shown to have the greatest potential.

Superhalogens as Building Blocks of Halogen‐Free Electrolytes in Lithium‐Ion Batteries

Alkali metal cations and halogen anions are well-known components of salts. New classes of molecules referred to as superalkalis and superhalogens exist whose properties resemble those of alkali and halogen atoms, respectively. The former have ionization potentials smaller than those of alkali atoms while the latter have electron affinities larger than those of halogen atoms. Using gradient-corrected density functional theory we have examined the possibility that a new class of salts, referred to as supersalts, could be synthesized with superalkalis and superhalogens as building blocks. The possibility that hyperhalogens can be synthesized by using superalkalis instead of alkali atoms as the core has also been examined. Examples of superalkalis (superhalogens) used in this study include Li3O, Cs2Cl, and Cs2NO3 (BF4, BeF3, and NO3). While supersalts are found to be stable, the ability of superalkalis to form as the core of hyperhalogens is limited due to their large size.

Santanab Giri

Papers

Update 2 of: Electrophilicity Index

Stability, reactivity, and aromaticity of compounds of a multivalent superatom.

Electrophilicity index within a conceptual DFT framework

Superhalogens as Building Blocks of Halogen‐Free Electrolytes in Lithium‐Ion Batteries

Superalkalis and superhalogens as building blocks of supersalts.