[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

The challenges for further development of Li rechargeable batteries for electric vehicles are reviewed. Most important is safety, which requires development of a nonflammable electrolyte with either a larger window between its lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) or a constituent (or additive) that can develop rapidly a solid/ electrolyte-interface (SEI) layer to prevent plating of Li on a carbon anode during a fast charge of the battery. A high Li-ion conductivity (σ Li > 10 ―4 S/cm) in the electrolyte and across the electrode/ electrolyte interface is needed for a power battery. Important also is an increase in the density of the stored energy, which is the product of the voltage and capacity of reversible Li insertion/extraction into/from the electrodes. It will be difficult to design a better anode than carbon, but carbon requires formation of an SEI layer, which involves an irreversible capacity loss. The design of a cathode composed of environmentally benign, low-cost materials that has its electrochemical potential μ C well-matched to the HOMO of the electrolyte and allows access to two Li atoms per transition-metal cation would increase the energy density, but it is a daunting challenge. Two redox couples can be accessed where the cation redox couples are "pinned" at the top of the O 2p bands, but to take advantage of this possibility, it must be realized in a framework structure that can accept more than one Li atom per transition-metal cation. Moreover, such a situation represents an intrinsic voltage limit of the cathode, and matching this limit to the HOMO of the electrolyte requires the ability to tune the intrinsic voltage limit. Finally, the chemical compatibility in the battery must allow a long service life.

Challenges for Rechargeable Li Batteries

https://zenodo.org/record/1258475/files/article.pdf

Electron transfers in chemistry and biology

2.1. Solvents 4307 2.1.1. Propylene Carbonate (PC) 4308 2.1.2. Ethers 4308 2.1.3. Ethylene Carbonate (EC) 4309 2.1.4. Linear Dialkyl Carbonates 4310 2.2. Lithium Salts 4310 2.2.1. Lithium Perchlorate (LiClO4) 4311 2.2.2. Lithium Hexafluoroarsenate (LiAsF6) 4312 2.2.3. Lithium Tetrafluoroborate (LiBF4) 4312 2.2.4. Lithium Trifluoromethanesulfonate (LiTf) 4312 2.2.5. Lithium Bis(trifluoromethanesulfonyl)imide (LiIm) and Its Derivatives 4313

/pdf/nonaqueous-liquid-electrolytes-for-lithium-based-uxm5ffbi18.pdf

Nonaqueous liquid electrolytes for lithium-based rechargeable batteries.

6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Thermodynamics serves several functions for chemistry and ita sister sciences and technologies. The first of these historically, and still one of the most important, is the provision of limits on the performance of proceases and devices. The very origins of thermodynamics developed from the creative ways people addressed the problem of how beat to pump water out of mines.’ The provision of limits of performance is the main concern of the work we describe here. Research during the past 9 years has led to new ways of finding natural bounds on performance under the constraint that the system operate at a nonzero rate, thereby giving more realistic bounds than those derived from reversible processes. Some approaches tell us only the limits; others tell us also the process that would yield those limits. Frequently, we can infer how the lower bound on the energy we pay for operating at a nonzero rate depends on that rate of operation. There even exist processes for which no zero-rate reversible counterpart exists.2

/pdf/thermodynamics-for-processes-in-finite-time-3xs8qhe9go.pdf

Thermodynamics for Processes in Finite Time

We show that theoretical microscopic titration curves (THEMATICS) can be used to identify active-site residues in proteins of known structure. Results are featured for three enzymes: triosephosphate isomerase (TIM), aldose reductase (AR), and phosphomannose isomerase (PMI). We note that TIM and AR have similar structures but catalyze different kinds of reactions, whereas TIM and PMI have different structures but catalyze similar reactions. Analysis of the theoretical microscopic titration curves for all of the ionizable residues of these proteins shows that a small fraction (3–7%) of the curves possess a flat region where the residue is partially protonated over a wide pH range. The preponderance of residues with such perturbed curves occur in the active site. Additional results are given in summary form to show the success of the method for proteins with a variety of different chemistries and structures.

https://www.pnas.org/content/pnas/98/22/12473.full.pdf

THEMATICS: a simple computational predictor of enzyme function from structure.

The advent of lithium-ion or rocking chair rechargeable battery technology has severely stretched the anodic limits of common nonaqueous electrolytes. Salts of the form 1,2-dimethyl-3-propylimidazolium X [where X = AsF{sub 6}{sup {minus}}, PF{sub 6}{sup {minus}}, (CF{sub 3}SO{sub 2}){sub 2}N{sup {minus}}, and (CF{sub 3}SO{sub 2}){sub 3}C{sup {minus}}] were prepared and purified. Linear sweep voltammetry was conducted at 80 C, a temperature at which all four salts were molten, at Pt, W, and glassy carbon working electrodes. The authors found that the intrinsic anodic stability of these anions was in the order (CF{sub 3}SO{sub 2}){sub 3}C{sup {minus}} > (CF{sub 3}SO{sub 2}){sub 2}N{sup {minus}} {approximately} AsF{sub 6}{sup {minus}} > PF{sub 6}{sup {minus}}. These experimental solution-phase oxidation potentials correlated well with gas-phase highest occupied molecular orbital energies calculated by an ab initio technique.

https://iopscience.iop.org/article/10.1149/1.1836540/pdf

The Intrinsic Anodic Stability of Several Anions Comprising Solvent‐Free Ionic Liquids

In this paper we report the results of model calculations of the nuclear potential surfaces of van der Waals complexes consisting of large aromatic molecules and rare-gas (R) atoms. These potentials were constructed as a superposition of pairwise atom-atom potentials, the R-carbon atom pair potentials being taken from heats of adsorption of rare-gas atoms on graphite, while the R-hydrogen atom pair potentials are estimated by using empirical combination rules. The binding energies of the tetracene (T) complexes TRI are 0.7 kcal mol-' for Ne, 1.5 kcal mol-' for Ar, 1.8 kcal mol-' for Kr, and 2.2 kcal mol-' for Xe, while the equilibrium distance between R and the molecular plane of tetracene is 3.0 A for Ne, 3.45 A for Ar, 3.5 A for Kr, and 3.7 A for Xe. Low-frequency, large-amplitude motion of the R atoms parallel to the molecular plane along the long molecular axis is predicted for TR, and TR2 complexes. The potential for TRI along the long molecular axis has a symmetric double-well form, giving rise to a "tunneling-type'' motion of the R atom. For the TR2 complexes, the configuration with two R atoms located on the same side of the aromatic molecule is energetically favored over that with the two R atoms on opposite sides. No chemical isomers are expected to exist for the TRI and TR2 complexes, while for TR,, complexes with n 1 3 the possibility of the existence of two or more nearly isoenergetic isomers is indicated. The applications and implications of these data for the elucidation of some features of excited-state energetics and dynamics of such van der Waals complexes are considered. van der Waals (vdW) molecules'" are weakly bound molecular complexes held together by attractive (eg, dispersive, electrostatic, charge transfer, hydrogen bonding) interactions between closed- shell atoms or molecules. The primary characteristics of vdW molecules'd are their low (10-1000 cm-I) dissociation energies, the large length of the vdW bond, and the retention of many of the individual properties of the molecular constituents within the vdW complex. During the last few years remarkable progress was achieved in the understanding of the many facets of these interesting systems. These advances were initiated by the utili- zation of supersonic free expansion^^.^ to prepare a variety of fascinating vdW molecules, whose structure, energetics, and dy- namics were explored. The elucidation of the structure, the mapping of the potential surface, and the determination of the energetics of vdW molecules pertain to the basic understanding of intermolecular interactions in chemistry. In this context the ground-state properties of a variety of molecules, e.g., (HF)2,7 ArHF: ArHC1,9 ArHBr,l0 KrHCI," XeHC1,I2 ArCIF," ArOC- S," and the benzene dimer3 were investigated. Studies of in- tramolecular dynamics of vdW molecules in vibrationally excited or electronically vibrationally excited states provided central in- formation on reactive vibrational predissocation processes,57 this being relevant for establishing the general features of intramo- lecular vibrational energy flow in weakly coupled molecular systems. Intramolecular dynamical processes in a variety of vdW molecules, e.g., RIz (R = He, Ne, and Ar),'>'' (C12)2,18 (N2O)2,I9 (NH3)r20 and the ethylene dimer2' were recently explored both experimentally'52' and theoretically.6 The understanding of the reactive and nonreactive dynamics in vdW complexes requires detailed information on potential surfaces. The general conceptual framework advanced for the elucidation of the structural and energetic features of all these small and medium-sized vdW complexes mentioned above rests on a microscopic approach, taking advantage of the advanced techniques of molecular spec- tro~copy~~~~-" to probe the molecular equilibrium configuration, the details of nuclear motion, and the binding energies. This general approach may require some gross modifications when the structure, energies, and dynamics of very large vdW complexes will be considered. Recently, there have been experimental st~dies~~-~~ of very large vdW complexes consisting of aromatic molecules, such as anthracene, tetracene, pentacene, and ovalene

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Model Calculations of Potential Surfaces of van der Waals Complexes Containing Large Aromatic Molecules

The production of work in finite time from a reservoir with finite heat capacity is studied. A model system, for which the only irreversibilities result from finite rates of heat conduction, is adopted. The maximum work obtainable in finite time from such a system is derived, and is found to be strongly dependent upon the reservoir heat capacity. The cycle producing the maximum work is derived for an arbitrary one‐component working fluid; no equation of state is assumed. In the optimum cycle, when the working substance is in contact with a finite reservoir, then the temperature of the working fluid is an exponential function of time and the entropy of the working substance is a linear function of time. While the maximum work obtainable in a single fixed‐time cycle is a strictly increasing function of the reservoir heat capacity, the efficiency (work produced/heat put in) is a strictly decreasing function of the reservoir heat capacity, for the model system with a finite hot reservoir and an infinite cold ...

Mary Jo Ondrechen

Papers

Thermodynamics for Processes in Finite Time

THEMATICS: a simple computational predictor of enzyme function from structure.

The Intrinsic Anodic Stability of Several Anions Comprising Solvent‐Free Ionic Liquids

Model Calculations of Potential Surfaces of van der Waals Complexes Containing Large Aromatic Molecules

The generalized Carnot cycle: A working fluid operating in finite time between finite heat sources and sinks