Quantum structures

B3.2 Quantum structural methods for the solid state and surfaces... 

Computational solid-state physics and chemistry are vibrant areas of research. The all-electron methods for high-accuracy electronic stnicture calculations mentioned in section B3.2.3.2 are in active development, and with PAW, an efficient new all-electron method has recently been introduced. Ever more powerfiil computers enable more detailed predictions on systems of increasing size. At the same time, new, more complex materials require methods that are able to describe their large unit cells and diverse atomic make-up. Here, the new orbital-free DFT method may lead the way. More powerful teclmiques are also necessary for the accurate treatment of surfaces and their interaction with atoms and, possibly complex, molecules. Combined with recent progress in embedding theory, these developments make possible increasingly sophisticated predictions of the quantum structural properties of solids and solid surfaces. 

The question of whether the bandgap of the quantum structures is direct or indirect has been discussed by several authors. However, it has been pointed out that the electron and hole wave functions are spread in k space, breaking the... 

A DB at the quantum structure surface is expected to efficiently suppress visible luminescence. 

B. W. Shore. Manipulating Quantum Structures Using Laser Pulses. Cambridge University Press, Cambridge (2011). 

Focusing now our attention to our set of (t2g )3 states we observe that 2D and S are the MQ = 0 components of a quasi-spin singlet while 2P is the Mc = 0 component of a quasi-spin triplet. The full quantum structure of the (t2g)3 multiplets thus involves seven labels QMQSLTMsMry, albeit the Me label is redundant since all states share the same MQ value. 

The quantum structure and properties of empty fullerenes C are extensively studied with the help of the powerful photoelectron (photoabsorption) spectroscopy technique [2,11]. As for the spectroscopy of gas phase doped... 

Sakuma, T., Sheppard, L.M., and Ikuhara, Y., (eds) (2000), Grain Boundary Engineering in Ceramics From Grain Boundary Phenomena to Grain Boundary Quantum Structures, Ceramic Transactions, 118, Westerville, OH, The American Ceramic Society. 

Jozef T. Devreese and Piet Van Camp, Electronic Structure, Dynamics, and Quantum Structural Properties of Condensed Matter. Proceedings of the Antwerp Advanced Study Institute held July 16-27, 1984, Priorij Corsendonk, Belgium, in NATO Advanced Science Institutes, Series B Physics, Vol. 121, Plenum, New York, 1985. 

There are large lattice mismatches between GaN, InN and AIN. Therefore, realisation of high quality heterostructures and quantum structures free of dislocations is one of the important issues. 

Karl Unterrainer, Photon-Assisted Tunneling in Semiconductor Quantum Structures P. Haring Bolivar, T. Dekorsy, and H. Kurz, Optically Excited Bloch Oscillations-Fundamentals and Application Perspectives... 

The only type of chemical reaction we are likely to ever be able to solve rigorously in a quantum mechanical way is a three-body reaction of the type A+BC - AB+C. (See Fig. 5.) The input information to the dynamicist is the potential energy surface computed by the quantum structure chemist. Given this potential surface, we treat the nuclear collision dynamics using Schrodinger s equation to model the chemical reaction process. 

Louie, S. G. (1985) in Electronic Structure, Dynamics, and Quantum Structural Properties of Condensed Matter (J. T. Devreese and P. 

Figure 18 A structure map (or quantum structural diagram, QSD) for the AB octets using Villars indices. (Reproduced by permission of Elsevier from Villars )...

Industry is highly interested in new materials that possess new or improved properties. The use of structure maps and other diagrammatic tools aid in this quest. Below are described the uses of such maps in the search for property-specific materials. In the sections on stable quasicrystals, high-Tc superconductors, and ferroelectrics, the applications of the quantum structural diagrams (QSD) described above will be used. In these classes of materials, the analysis starts with the compilation of the diagrammatic coordinates as described in equation (6). For these unusual types of order, the existence of diagrammatic regularities implies, at least, that the same factors that control local structure and stability in ordinary compounds also determine the tendency to these types of order and probably a coimection as well. 

Figure 26 Plots for 67 high-Tc superconductors (a) AX — AR quantum structural diagrams, and (b) Mathias plot 7 versus N. See text for information on islands A, B, C. (Reproduced by permission of Academic Press from PlulhpsT )...

Nanocomposites in the form of superlattice structures have been fabricated with metallic, " semiconductor,and ceramic materials " " for semiconductor-based devices. " The material is abruptly modulated with respect to composition and/or structure. Semiconductor superlattice devices are usually multiple quantum structures, in which nanometer-scale layers of a lower band gap material such as GaAs are sandwiched between layers of a larger band gap material such as GaAlAs. " Quantum effects such as enhanced carrier mobility (two-dimensional electron gas) and bound states in the optical absorption spectrum, and nonlinear optical effects, such as intensity-dependent refractive indices, have been observed in nanomodulated semiconductor multiple quantum wells. " Examples of devices based on these structures include fast optical switches, high electron mobility transistors, and quantum well lasers. " Room-temperature electrochemical... 

A comparative molecular analysis study based on three-dimensional quantum structure-activity relationships was performed by Pajeva and Wiese [159] on 40 phenothiazines and structurally related drugs to predict their MDR modification. More than 350 theoretical models were derived and evaluated using steric, electrostatic and hydrophobic fields alone and in combination. All examined fields were found to contribute to MDR reversing activity, and their hydrophobic fields improved the correlative and predictive power of the models in all cases. The results point out the role of hydropho-bicity as a space-directed molecular property to explain the differences in anti-MDR activity of the drugs under study. 

But second and more important. Priest continues to endorse the inference that because certain properties are primary, they are explanatory. The behavior of matter "at each level may be explained in terms of the structure of the level below. Thus, the behavior of macroscopic bodies and their properties is explained in terms of the (primary) properties of its microscopic (atomic) parts" (Priest, 1989, p. 36). And the behavior of the microscopic parts, which are the bearers of the primary properties, is "explained in terms of their quantum states and properties" (Priest, 1989, p. 36). On the account I have offered, such talk is problematic. The "bare" quantum structure does not explain—all by itself—the microscopic primary property. Reference to the measurement technique must also be included. But perhaps even more important, as I alluded previously, even the quantum structure is not universal or intrinsic. One and the same hunk of matter can have quantum or classical microscopic properties, depending on the time scale of the measurement. It will be of little explanatory importance to refer to the "quantum states and properties" in most spectroscopic measurement situations. To be sure, quantum corrections can be added in if a finer level of explanation is desired, but the "bare" quantum structure doesn t even exist at common... 

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