| Fundamental Understanding and Theoretical Design of Novel Nanostructured Semiconductor Materials |
04 Jan 2012 |
6 pages |
| Authors:
Arthur J Freeman; Jung-Hwan Song; Haowei Peng; Min S Park; Julia Medvedeva; Miyoung Kim; In G Kim; Mercouri Kanatzidis; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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 | This research was for the fundamental understanding and theoretical design of novel nanostructured semiconductor materials with a potential impact in the areas of thermoelectrics, solar energy, and the role of impurities and embedded nanoparticles. The most challenging phase of the theoretical research was attacked so as to help understand the underlying fundamental electronic structures, find the key mechanism, and finally suggest design principles for desirable thermoelectric and solar energy materials. ... |
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| Multispectral Detector Based on Array of Carbon-Nanotube Quantum Wells |
30 Sep 2009 |
23 pages |
| Authors:
Serhii Shafraniuk; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The research efforts focused on comb arrays of carbon nanotube quantum wells exposed to external weak THz fields. Each of the individual well in the array had been independently controlled by a dc source-drain voltage and covered a narrow spectral sector within the THz domain diapason. The comb array consisted of two different types of carbon nanotube junctions: semiconducting tube junctions and the metallic tube junctions in the Tomonaga-Luttinger liquid ... |
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| Fundamental Electronic Structure Characteristics and Mechanical Behavior of Aerospace Materials |
APR 2008 |
22 pages |
| Authors:
Arthur J. Freeman; Oleg Y. Kontsevoi; Yuri N. Gornostyrev; Nadezhda I. Medvedeva; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| To fulfill the great potential of intermetallic alloys for high temperature structural applications, it is essential to understand the mechanisms controlling their mechanical behavior on the microscopic level. We focus on the mechanical behavior of homogeneous intermetallics with LI 2 and B2 structures, two-phase `ly' alloys, and bcc transition metals and their alloys. Based on highly-accurate total energy calculations and large-scale Peierls-Nabarro and atomistic modeling, we investigated the relation between ... |
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| Security of Y-00 and Similar Quantum Cryptographic Protocols |
16 NOV 2004 |
10 pages |
| Authors:
Horace P. Yuen; Prem Kumar; Eric Corndorf; Ranjith Nair; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| It is claimed in Phys. Lett. A by T. Nishioka et al. [327 (2004) 28-32] that the security of Y-00 is equivalent to that of a classical stream cipher. In this paper it is shown that the claim is false in either the use of Y-00 for direct encryption or key generation, in all the parameter ranges it is supposed to operate including those of the experiments reported thus far. ... |
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| Predicting Aspects of Mechanical Behavior via Fundamental Electronic Structure Characteristics of Homogeneous Phases and Intrinsic Interfaces |
29 FEB 2004 |
9 pages |
| Authors:
Authur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| To fulfill the great potential of intermetallic alloys for high temperature structural applications, it is necessary to understand the mechanisms controlling their mechanical behavior on the microscopic level, including such key phenomena as dislocation structure and mobility. We focused on the mechanical behavior of homogeneous intermetallics with L1(sub 2) and B2 structures and on two-phase gamma/gamma' alloys. Based on highly-accurate total energy calculations and large-scale Peierls-Nabarro modeling, the relation between ... |
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| Nonthermal Emission from the Arches Cluster (G0.121+0.017) and the Origin of gamma-Ray Emission from 3EG J1746-2851 |
20 JUN 2003 |
5 pages |
| Authors:
F. Yusef-Zadeh; M. Nord; M. Wardle; C. Law; C. Lang; T. J. Lazio; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| High-resolution Very Large Array observations of the Arches cluster near the Galactic center show evidence of continuum emission at gamma = 3.6, 6, 20, and 90 cm. The continuum emission at gamma = 90 cm is particularly striking because thermal sources generally become optically thick at longer wavelengths and fall off in brightness, whereas nonthermal sources increase in brightness. It is argued that the radio emission from this unique source ... |
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| Bonding, Energetics and Mechanical Properties of Intermetallics |
JUN 2001 |
10 pages |
| Authors:
Arthur J. Freeman; Yu N. Gornostyrev; O. N. Mryasov; O. Y. Kontsevoi; N. I. Medvedeva; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| To fulfill the great potential of intermetallic alloys for use in high temperature structural applications, it is necessary to understand on the microscopic level the mechanisms controlling their mechanical behavior, including such key phenomena as dislocation structure and mobility, crack blunting and propagation, the role and the effect of alloying additions: while they have been characterized by mesoscopic length and energy scales, they are determined on the microscopic level by ... |
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| Strained and Unstrained Bi(1-x)Sb(x) Superlattice Thermoelectrics |
19 MAY 2001 |
72 pages |
| Authors:
John B. Ketterson; Arthur J. Freeman; Jerry R. Meyer; George K. Wong; Antonio DiVenere; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The electronic band structure of artificially ordered superlattice alloys (SLA) of Bi and Sb, prepared by alternately depositing thin layers of Bi and Sb as a superlattice, could be modified from a semimetal to a semiconductor by changing the period of the superlattice. This new SLA opens a possibility to engineer an alloy material to get more desirable thermoelectric properties, because a thermal conductivity reduction, due to an increase in ... |
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| Bonding, Energetics and Mechanical Properties of Intermetallics |
NOV 2000 |
10 pages |
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| In high-temperature intermetallics, dislocations play an especially important role for understanding mechanisms of their deformation and fracture behavior and anomalous mechanical response which are still far from being well understood and remain a challenge to theoretical explanation. Progress in this complex area requires understanding such key phenomena as dislocation structure and mobility, and crack blunting and propagation: while they have been characterized by mesoscopic length and energy scales, they are ... |
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| Radio Continuum Emission from the Central Stars of M20, and the Detection of a New Supernova Remnant Near M20 |
10 SEP 2000 |
10 pages |
| Authors:
F. Yusef-Zadeh; Mark Shure; Mark Wardle; N. Kassim; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The Trifid Nebula (M20) is a well-known prominent optical H II region trisected by obscuring dust lanes. Radio continuum VLA observations of this nebula show free-free emission at wavelength = 3.6 and 6 cm from three stellar sources lying close to the O7 V star at the center of the nebula. We argue that neutral material associated with these stars is photoionized externally by the UV radiation from the hot ... |
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| Journal of Magnetism and Magnetic Materials. Volumes 198-199, 1 June 1999 |
01 JUN 1999 |
795 pages |
| Authors:
A. J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The Journal of Magnetism and Magnetic Materials provides an important forum for the disclosure and discussion of original contributions covering the whole spectrum of topics, from basic magnetism to the technology and applications of magnetic materials and magnetic recording. The journal encourages greater interaction between the basic and applied subdisciplines of magnetism, with short but comprehensive review articles, a rapid publication channel with Letters to the Editors, and a section ... |
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| Bonding, Energetics and Mechanical Properties of Intermetallics |
15 JUL 1998 |
27 pages |
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The objective of this research was to investigate fundamental aspects of the fracture and deformation behavior of ordered intermetallic aerospace alloys on the basis of the ab-initio determination of the parameters needed for further (1) model theoretical, (2) band structure and (3) chemical bonding analyses. The research was targeted at investigating the microscopic mechanisms governing the deformation and fracture behavior of intermetallic alloys in order to ... |
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| OSSE Limits on Pre- and Post-Burst Emission (Preprint) |
12 JUL 1995 |
5 pages |
| Authors:
S. M. Matz; J. E. Grove; W. N. Johnson; J. D. Kurfess; G. H. Share; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The existence of either pre- or post-burst emission can provide substantial new information about the burst source and its local environment. We have data from several events serendipitously in or near the OSSE field of view at the time of the burst. We present pre- and post-burst flux limits from one such event, GRB 940301. The OSSE data for other periods when scheduled observations have included burst locations will enable ... |
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| BATSE/OSSE Rapid Burst Response |
12 JUL 1995 |
5 pages |
| Authors:
S. M. Matz; J. E. Grove; W. N. Johnson; J. D. Kurfess; G. H. Share; G. J. Fishman; C. A. Meegan; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The BATSE and OSSE instrument teams have modified ight software to promptly (within 2 min of trigger) slew the OSSE detectors to burst locations determined on-board by BATSE. This enables OSSE to make sensitive searches for prompt and delayed post-burst line and continuum emission above 50 keV. In the best cases our sensitivity will be more than an order of magnitude better than any other search in this energy range. ... |
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| Structural and Electronic Properties of adsorbates on Semiconductors, Metal-Semiconductor Interfaces and Semiconductor Heterojunctions |
07 MAR 95 |
10 pages |
| Authors:
A. J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| Studies of the electronic structure of adsorbates on metal- semiconductor and semiconductor-semiconductor interfaces and semiconductor surfaces were carried out using the molecular cluster LCAO-DVM method (as developed into the DMo1 program) also in a full potential local (spin) density approach. The new capability of DMo1 to calculate atomic forces allows automatic geometry optimization; and allowed us to study atomic relaxation and reconstruction at the surfaces and interfaces with and without ... |
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| Computer-Aided Systems Design of Advanced Steels |
95 |
14 pages |
| Authors:
Charles J. Kuehmann; Gregory B. Olson; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The multi-institutional interdisciplinary research program of the Steel Research Group (SRG) has centered on the development of a systems approach for the design of advanced high performance steels using computer aided modelling. Initial long range studies involved the development of the theoretical foundations underlying strength, toughness, and hydrogen resistance. Mechanistic based computational models include the prediction of martensite start temperatures in high alloy steels, multicomponent coarsening kinetics in non-ideal non-dilute ... |
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| Cluster Models of Bulk, Surface, and Impurity Structure in Alpha- Alumina |
94 |
|
| Authors:
Donald E. Ellis; Jun Guo; Daniel J. Lam; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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 | Self-consistent field embedded cluster models have been used to study the electronic structure of bulk, surface, and impurity regions of alpha- alumina, Al2O3. First principles local density (LD) theory is used to make an expansion of one-electron wave functions in a linear combination of atomic orbitals which permits direct interpretation of binding and effective atomic configurations. The clusters are embedded self-consistently in the host lattice, so that all long-range potential ... |
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| Hard X-Ray Variability of Cygnus X-3 |
1994 |
5 pages |
| Authors:
S. M. Matz; D. A. Grabelsky; W. R. Purcell; M. P. Ulmer; W. N. Johnson; R. L. Kinzer; J. D. Kurfess; M. S. Strickman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The OSSE instrument on the Compton Gamma-Ray Observatory (GRO) made 4 observations of Cygnus X-3 between May 1991 and December 1992. OSSE observed a substantial change in the average hard X-ray flux, which has previously been observed to be stable (variations < 20%). Over a 2-3 day period the flux above ~50 keV decreased by roughly a factor of 3. This occurred about 15 days prior to a large radio ... |
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| High Quality Alpha-Si/Nb and Alpha-SiN/NbN Artificial Multilayers for Josephson Applications. |
1994 |
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| Authors:
J. Chen; E. D. Rippert; S. N. Song; M. P. Ulmer; J. B. Ketterson; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| A high resolution transmission electron microscopy study of multilayer films prepared by magnetron sputtering shows that the morphology of the growing interfaces in a-si/nb and a-sin/nbn multilayers is remarkably uniform and smooth; this is in contrast to the polycrystalline aln/nbn multilayers grown under similar conditions, which exhibit columnar grain structure with rough interfaces. for proper sputtering parameters, the amorphous layers seem to periodically restore a relatively smooth initial interface condition ... |
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| Gamma-Ray and Radio Observations of PSR B1509-58 |
06 MAY 1993 |
17 pages |
| Authors:
M. P. Ulmer; S. M. Matz; R. B. Wilson; M. J. Finger; K. S. Hagedon; D. A. Grabelsky; J. E. Grove; W. N. Johnson; R. L. Kinzer; J. D. Kurfess; W. R. Purcell; M. S. Strickman; V. M. Kaspi; S. Johnston; R. N. Manchester; A. G. Lyne; N. D'Amico; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| We report concurrent radio and gamma-ray observations of PSR B1509-58 carried out by the Parkes Radio Telescope and by the Burst and Transient Source Experiment (BATSE) and the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (CGRO-Gamma-ray light curves fitted at several energies between ~ 20-500 keV yield a phase offset with respect to the radio pulse that is independent of energy, with an average value 0.32 ... |
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| Effect of Stoichiometry on the Structural Properties and the Electronic Structure of Intermetallics: Anti-Phase Boundary Energies in FeAl and NiAl |
92 |
|
| Authors:
T. Hong; A. J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| As a possible means of alleviating the severe brittleness in the B2 compounds FeAl and NiAl, the all-electron self-consistent total energy linear muffin-tin orbital (LMTO) method was employed to investigate the possibility of lowering the anti-phase boundary (APB) energies by changing compositions in FeAl and NiAl; for APB's created in the regions with excess Fe (or Ni) atoms, APB energies for the model systems, Fe0.6Al0.4 and Ni0.6Al0.4, were found to ... |
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| Cohesive Properties, Electronic Structure, and Bonding Characteristics of RuAl--A Comparison to NiAl |
92 |
|
| Authors:
W. Lin; Jian-hua Xu; A. J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| Recent experiments on promising high-temperature aluminide intermetallic compounds discovered that, in contrast to NiAl, RuAl has critical slip systems that facilitate ductility under compression at room temperature; in order to understand this different mechanical property from a microscopic point of view, the cohesive and electronic properties of NiAl and RuAl have been studied by means of the first principles local density all- electron self-consistent linearized muffin-tin orbital (LMTO) and full-potential ... |
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| First Principles Calculation of the Elastic Constants of Intermetallic Compounds: Metastable Al3Li |
91 |
|
| Authors:
X. Q. Guo; R. Podloucky; A. J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| We report first principles local density calculations for the metastable Al3Li intermetallic compound with cubic Li(sub 2) crystal structure using the full-potential linearized augmented plane wave method; from the second derivative of the total energy function of volume, and generated tetragonal and trigonal lattice distortions, the elastic constants C11, C12, and C44 were derived yielding C11=158GPa, C12=29.4GPa, and C44=57.7GPa; because of the very high Young's modulus (E=141 GPa) compared, for ... |
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| Phase Stability and Role of Ternary Additions on Electronic and Mechanical Properties of Aluminum Intermetallics |
91 |
|
| Authors:
A. J. Freeman; T. Hong; W. Lin; Jian-hua Xu; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| First principles total energy local density method have addressed the problems of (i) bonding, cohesion and phase stability and (ii) the role of ternary additions, anti-phase boundaries (APB's) and other faults in determining the structural, electronic, and mechanical properties of aluminum intermetallic alloys; a key goal has been to attempt to understand, at the electronic level, fundamental quantities that may be related to the crucial brittleness vs. ductility issue in ... |
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| Crystal Structure, Phase Stability, and Electronic Structure of Ti-Al Intermetallics: Ti3Al |
91 |
|
| Authors:
T. Hong; T. J. Watson-Yang; X. Q. Guo; A. J. Freeman; T. Oguchi; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| A potentially useful high-temperature intermetallic compound Ti3Al is investigated theoretically by the self-consistent liner muffin-tin orbitals (LMTO) and full-potential linearized augmented-plane-wave (FLAPW) methods within the local-density approximation; structural properties were calculated for the naturally observed structure, DO(sub 19), and for two other similar structures, DO(sub 22) and L1(sub 2). |
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| Effect of Antiphase Boundaries on the Electronic Structure and Bonding Character of Intermetallic Systems: NiAl |
91 |
|
| Authors:
T. Hong; A. J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| All-electron self-consistent total-energy linear-muffin-tin-orbital calculations were used to study the origin of low ductility in Ni-Al based alloys in the B2 structure; antiphase boundary (APB) energies of 1/2 on ?110! and 1/2 on ?112! were calculated using a supercell approach; APB energy can be significantly reduced by substituting Ni or Al with V, Cr, or Mn at the APB interfacial planes. |
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| Quantum Mechanical Approach to Understanding Microstructural and Mechanical Properties of Intermetallics |
31 OCT 90 |
|
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| The primary goal of the proposed research was to study and develop alloying concepts for understanding intermetallic alloys as derived from a first principles quantum mechanical approach. Thus, a major part of our effort will be to study and determine ductilizing effects of alloying elements in several intermetallic compounds and to work closely with experimental efforts to evaluate the applicability of the theoretical approach to alloy design. Specifically, highly precise ... |
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| Cluster Models for Electronic Structure of Oxide Ceramics |
90 |
|
| Authors:
D. E. Ellis; J. Guo; D. J. Lam; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| Recent progress in using cluster models to calculate electronic structure of oxide ceramics such as transition-metal monoxides, zirconia, alpha- alumina, ruby, and copper-based superconducting oxides is reviewed. The self- consistent field local density theory is used to find potentials, energy levels, and wave functions for a fragment consisting of an N number of atoms embedded in the infinite solid. The single-particle spectra are compared with photoelectron and optical data, and ... |
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| Quantum Mechanical Approach to Understanding Structural, Electronic and Mechanical Properties of Intermetallics |
26 JAN 89 |
14 pages |
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| Our primary goal is to study and develop alloying concepts for understanding intermetallic alloys as derived from a highly precise quantum mechanical approach. Thus, a major part of our effort is to study and determine ductilizing effects and to work closely with experimental efforts to evaluate the applicability of the theoretical approach to alloy design. Specifically we have studied a number of materials problems to obtain first principles information of ... |
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| SMM Observations of Interstellar 26Al: A Status Report |
88 |
8 pages |
| Authors:
W. R. Purcell; M. P. Ulmer; G. H. Share; R. L. Kinzer; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| The discovery of radioactive Al 26 in the interstellar medium has provided direct evidence for the recent nucleosynthesis of intermediate-mass nuclei in the Galaxy. While modern nucleosynthesis theories suggest that Al 26 production may occur in a variety of astrophysical objects, they have not been able to identify the dominant production site of the observed Al 26. Observationally, the greatest hope for identifying its source is through a comparison of ... |
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| Electronically Induced Phase Transformation |
26 SEP 86 |
|
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
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| A new technique for determining the electronic structure of bulk solids has been developed by solving Poisson's equation for a general charge density and potential. All contributions to the potential are completely taken into account in the Hamiltonian matrix elements. The high accuracy of this approach allows us to go beyond traditional treatments and to consider the total energy which allows the accurate determination of structural information (lattice parameters, force ... |
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| Electronically Induced Phase Transformations |
30 NOV 1982 |
|
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| Our recent development of self-consistent local (spin) density energy band approaches have provided a powerful theoretical/computational tool for determining the electronic structure and properties of complex materials. The importance of charge transfer between constituent atom species has been demonstrated as has its inclusion by means of accurate self-consistent solutions. Some examples of areas in which progress has been achieved include: the high field superconductivity in Chevrel phase compounds; the unusual ... |
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| Electronically Induced Phase Transformations |
30 NOV 1981 |
11 pages |
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| The electronic interactions responsible for the observed electronically induced phase transformations in several important classes of materials were investigated theoretically in close collaboration with experimental programs at other institutions. These include the high field superconductivity of Chevrel phase compounds and the first theoretical demonstration that the Jaccarino-Peter mechanism is responsible for the large increase in the upper critical field when large concentrations of Eu magnetic impurities are added to SnMo6S8, ... |
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| Electronically Induced Phase Transformations |
DEC 80 |
71 pages |
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| The electronic interactions responsible for the observed electronically induced phase transformations in several important classes of materials were investigated theoretically in close collaboration with experimental programs at other institutions. These include destruction of superconductivity and onset of a normal magnetic state at low temperatures in ternary rare-earth superconducting compounds and the possible occurrence of a new mixed phase, the origin of the phase transition to the superconducting phase in the ... |
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| Investigation of Nematic Ordering Using Electric-Field-Induced Second-Harmonic Generation, |
31 OCT 1978 |
|
| Authors:
S. K. Saha; George K. Wong; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
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| Electronically Induced Phase Transformations. |
OCT 1978 |
|
| Authors:
Arthur J. Freeman; NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
|
| The electronic interactions responsible for the observed electronically induced phase transformations in several important classes of materials are being investigated theoretically in close collaboration with experimental programs at other institutions. These include destruction of superconductivity and onset of a normal magnetic state at low temperatures in ternary rare-earth superconducting compounds, charge density waves in layered transition metal dichalcogenides, origin of phonon anomalies in Pd and Pt metals, local density formalism ... |
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