Electronic Structures for (Si)m (GaP)n Superlattices

1991 ◽  
Vol 220 ◽  
Author(s):  
P. J. Lin-Chung
Keyword(s):  
Band Gap ◽  
Electronic Structures ◽  
Tight Binding ◽  
The Other ◽  
Band Structures ◽  
Other Hand

ABSTRACTThis paper reports on a tight-binding calculation of the band structures of the Si-GaP superlattice (SL) systems with emphasis on the results of the band gap properties. This calculation finds that the SLs grown onto the [110] or [111] oriented substrate do not produce direct gap materials. On the other hand, some of the [001] oriented SLs become direct gap materials when either an interface (IF) state is created at the P and Si IF, or a confined state in the Si occurs with only Ga and Si atoms forming all the IF.

OPTICAL PROPERTIES OF FUNCTIONALIZED POLYTHIOPHENES

2005 ◽  
Vol 19 (32) ◽  
pp. 4645-4676 ◽  
Author(s):  
N. SOMANATHAN ◽  
S. RADHAKRISHNAN
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Functional Groups ◽  
Thiophene Ring ◽  
Point Of View ◽  
The Other ◽  
Emission Characteristics ◽  
Polymeric Structure ◽  
Other Hand

This review focuses on the interrelation between the influences of polymeric structure on the optical properties of polythiophene — a versatile polymer for opto-electronic applications. From the application's point of view, the polymer should either be melt- or solution-processible. Functionalization of polythiophenes really helps for the above. On the other hand, the functionalization at the 3 and/or 4 position of the thiophene ring modifies the band gap of the polymer, which in turn, modifies photo absorption, photo- and electro-emission characteristics of polythiophenes. The present work reviews the influence of the optical properties of polythiophene on the different functional groups present in the thiophene ring.

scholarly journals Persistent Current in Metallic Rings and Cylinders

2009 ◽  
Vol 155 ◽  
pp. 87-104 ◽  
Author(s):  
Santanu K. Maiti
Keyword(s):  
Chemical Potential ◽  
Tight Binding ◽  
Persistent Current ◽  
The Other ◽  
Magnetic Response ◽  
Low Field ◽  
Other Hand ◽  
Fixed Sign ◽  
Metallic Rings

We explore the behavior of persistent current and low-field magnetic response in mesoscopic one-channel rings and multi-channel cylinders within the tight-binding framework. We show that the characteristic properties of persistent current strongly depend on total number of electrons , chemical potential μ, randomness and total number of channels. The study of low-field magnetic response reveals that only for one-channel rings with fixed , sign of the low-field currents can be predicted exactly, even in the presence of disorder. On the other hand, for multi-channel cylinders, sign of the low-field currents cannot be mentioned exactly, even in the perfect systems with fixed as it significantly depends on the choices of , μ, number of channels, disordered configurations, etc.

Design of Novel Conjugated Polymer Poly(cyclopenta-1,3-Diene)

2010 ◽  
Vol 663-665 ◽  
pp. 662-665
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma
Keyword(s):  
Band Gap ◽  
Electronic Structures ◽  
Conjugated Polymer ◽  
Tight Binding ◽  
Optoelectronic Devices ◽  
Extended Hückel

A novel linear conjugated polymer, poly(cyclopenta-1,3-diene), is designed. The electronic structures of poly(cyclopenta-1,3-diene) is calculated with extended Hückel tight binding program. The calculated band gap of the polymer is about 1.1 eV, which suggests this kind of conjugated polymer can be used in infrared optoelectronic devices.

Electronic structures and optical properties of α-Fe2O3-xSex alloys for solar absorber

2015 ◽  
Vol 29 (12) ◽  
pp. 1550050 ◽  
Author(s):  
Congxin Xia ◽  
Yu Jia ◽  
Qiming Zhang
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Electronic Structures ◽  
Visible Range ◽  
Optical Absorption Edge ◽  
Band Structures ◽  
Solar Absorber ◽  
Direct Band ◽  
Gap Values

The band structures and optical properties of α- Fe 2 O 3-x Se x alloys are studied by means of first-principles methods, considering different Se contents x. Numerical results show that Se content has an obvious influence on band structures and optical properties of α- Fe 2 O 3-x Se x alloys. The band gap values of α- Fe 2 O 3-x Se x alloys decrease monotonically when Se concentrations increase, resulting in an obvious increase of the optical absorption edge in the visible range. In particular, our results show that α- Fe 2 O 3-x Se x alloys have the direct band gap properties with band gap values when Se content x ≈ 0.17, which is beneficial to solar cell applications.

scholarly journals STRUCTURAL DISTORTION IN LUDWIGITES

2013 ◽  
Vol 27 (17) ◽  
pp. 1350131 ◽  
Author(s):  
E. VALLEJO ◽  
G. CALDERON
Keyword(s):  
Order Parameter ◽  
Tight Binding ◽  
The Other ◽  
Structural Distortion ◽  
Itinerant Electrons ◽  
Other Hand ◽  
Infinite Repulsion

Structural distortion in a three-leg-ladder is studied in connection with Ludwigites, in particular the Fe and Co homometallic ones. Static impurities in t2g-orbitals as infinite repulsion potentials randomly located in the three-leg-ladder and a Su–Schrieffer–Heeger like tight-binding Hamiltonian are proposed and discussed. It is found that such potentials block itinerant electrons and diminish a structural staggered order parameter, related with structural distortion, as 3-M being M the number of impurities. This diminution is in detriment of Peierls like distortion that occurs in these ladders as in the case of Fe -Ludwigite. On the other hand, this diminution could explain the lack of structural distortion as in the case of Co -Ludwigite.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

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