CH 233H Final Exam Tuesday, June 9, 2015
... -Hydrogenation of benzene to cyclohexane -Hydrogenation of 1,3-cyclohexadiene to cyclohexane -Hydrogenation of cyclohexene to cyclohexane The easiest way is to calculate DGf° (298K) for each compound noted above. Then calculate DGr° (298K) for each reaction (products – reactants): Benzene to cyclohe ...
... -Hydrogenation of benzene to cyclohexane -Hydrogenation of 1,3-cyclohexadiene to cyclohexane -Hydrogenation of cyclohexene to cyclohexane The easiest way is to calculate DGf° (298K) for each compound noted above. Then calculate DGr° (298K) for each reaction (products – reactants): Benzene to cyclohe ...
Spin correlations in frustrated magnets with orbital
... published magnetic exchange model was unable to account for our data and a new model is proposed. This magnetic exchange model distinguishes between the two candidate orbital ordering models. The perovskite orthovanadates, RVO3 (R = rare earth or Y), display a variety of commensurate magnetic struct ...
... published magnetic exchange model was unable to account for our data and a new model is proposed. This magnetic exchange model distinguishes between the two candidate orbital ordering models. The perovskite orthovanadates, RVO3 (R = rare earth or Y), display a variety of commensurate magnetic struct ...
How do atoms arrange themselves to form solids? • Fundamental
... ¾ Metals are usually (poly)crystalline; although formation of amorphous metals is possible by rapid cooling ¾ As we learned in Chapter 2, the atomic bonding in metals is non-directional ⇒ no restriction on numbers or positions of nearest-neighbor atoms ⇒ large number of nearest neighbors and dense a ...
... ¾ Metals are usually (poly)crystalline; although formation of amorphous metals is possible by rapid cooling ¾ As we learned in Chapter 2, the atomic bonding in metals is non-directional ⇒ no restriction on numbers or positions of nearest-neighbor atoms ⇒ large number of nearest neighbors and dense a ...
the application of electron spin resonance
... the direct absorption curve, but as its first derivative. A typical resonance lineshape is illustrated in Fig. 2a. So far we have considered only a single unpaired electron whose interaction with its environment may be neglected. In most cases, however, the unpaired electrons are influenced by other ...
... the direct absorption curve, but as its first derivative. A typical resonance lineshape is illustrated in Fig. 2a. So far we have considered only a single unpaired electron whose interaction with its environment may be neglected. In most cases, however, the unpaired electrons are influenced by other ...
Geometrical frustration
In condensed matter physics, the term geometrical frustration (or in short: frustration) refers to a phenomenon, where atoms tend to stick to non-trivial positions or where, on a regular crystal lattice, conflicting inter-atomic forces (each one favoring rather simple, but different structures) lead to quite complex structures. As a consequence of the frustration in the geometry or in the forces, a plenitude of distinct ground states may result at zero temperature, and usual thermal ordering may be suppressed at higher temperatures. Much studied examples are amorphous materials, glasses, or dilute magnets.The term frustration, in the context of magnetic systems, has been introduced by Gerard Toulouse (1977). Indeed, frustrated magnetic systems had been studied even before. Early work includes a study of the Ising model on a triangular lattice with nearest-neighbor spins coupled antiferromagnetically, by G. H. Wannier, published in 1950. Related features occur in magnets with competing interactions, where both ferro- as well as antiferromagnetic couplings between pairs of spins or magnetic moments are present, with the type of interaction depending on the separation distance of the spins. In that case commensurability, such as helical spin arrangements may result, as had been discussed originally, especially, by A. Yoshimori, T. A. Kaplan, R. J. Elliott, and others, starting in 1959, to describe experimental findings on rare-earth metals. A renewed interest in such spin systems with frustrated or competing interactions arose about two decades later, beginning in the 70s of the 20th century, in the context of spin glasses and spatially modulated magnetic superstructures. In spin glasses, frustration is augmented by stochastic disorder in the interactions, as may occur, experimentally, in non-stoichiometric magnetic alloys. Carefully analyzed spin models with frustration include the Sherrington-Kirkpatrick model, describing spin glasses, and the ANNNI model, describing commensurability magnetic superstructures.