Zero-Point Effects in Heisenberg Antiferromagnets with Arbitrary Range of Interaction

1972 ◽  
Vol 50 (23) ◽  
pp. 2991-2996 ◽  
Author(s):  
M. F. Collins ◽  
V. K. Tondon
Keyword(s):  
Ground State ◽  
State Energy ◽  
Correction Term ◽  
Zero Point ◽  
Face Centered Cubic ◽  
Heisenberg Antiferromagnet ◽  
Body Centered Cubic ◽  
Cubic Lattices ◽  
Simple Cubic ◽  
Face Centered

The ground state energy, spin-wave energy, and sublattice magnetization have been calculated for a Heisenberg antiferromagnet at the absolute zero of temperature. The treatment extends the earlier work of Anderson, Kubo, and Oguchi to apply for any two-sublattice antiferromagnet with arbitrary range of interaction. It is shown that for each exchange interaction there is a different characteristic correction term to the energies. Explicit calculations are made of these terms for the simple cubic, body-centered cubic, and face-centered cubic lattices, with both first- and second-neighbor interactions. Applications are also made to NiO and MnO. An extra term in the magnetization series beyond that given by earlier workers is derived.

Enhancement Of Power Factor In A Thermoelectric Composite With A Periodic Microstructure

2000 ◽  
Vol 626 ◽  
Author(s):  
Leonid G. Fel ◽  
Yakov M. Strelniker ◽  
David J. Bergman
Keyword(s):  
Thermoelectric Power ◽  
Power Factor ◽  
The Other ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
High Quality ◽  
Thermoelectric Power Factor ◽  
Simple Cubic ◽  
Periodic Microstructures ◽  
Face Centered

ABSTRACTThe thermoelectric power factor has been calculated for a two-constituent composite medium, where one constituent is a “high quality thermoelectric” while the other constituent is a “benign metal”, with large electrical and thermal conductivities but poor thermoelectric properties. It was recently discovered that, in such a mixture, the power factor could be greatly enhanced by an appropriate choice of microstructure. Here we report on a study of three periodic microstructures with cubic point symmetry under rotations: simple cubic (SC), body centered cubic (BCC), and face centered cubic (FCC) arrays of identical spheres of the benign metal embedded in the high quality thermoelectric host. We show detailed results for these microstructures in the case where the benign metal constituent is Copper, while the high quality thermoelectric constituent is the thermoelectric alloy (Bi2Te3)0.2 (Sb2Te3)0.8.

On the new structural phases in Al65Cu20Cr15 quasicrystalline alloy

1995 ◽  
Vol 10 (8) ◽  
pp. 1905-1912 ◽  
Author(s):  
Varsha Khare ◽  
N.P. Lalla ◽  
R.S. Tiwari ◽  
O.N. Srivastava
Keyword(s):  
Metastable Phase ◽  
Structural Characteristics ◽  
Icosahedral Phase ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Structural Variants ◽  
Simple Cubic ◽  
Face Centered ◽  
Specific Orientation

The quasicrystalline (qc) alloy Al65Cu20Cr15, unlike its Ru- and Fe-bearing counterparts like Al65Cu20Ru15 and Al65Cu20Fe15, is a metastable phase. This qc alloy has been shown to possess several structural variants and curious structural characteristics. We have investigated the qc alloy Al65Cu20Cr15 with special reference to the possible occurrence of new structural variants. TEM exploration of the as-quenched qc alloy has indeed revealed the existence of several new phases. These are (i) body-centered cubic (bcc) (a = 12.60 Å, disordered) and simple cubic (s.c.) (a = 12.60 Å, ordered), which are the 1/1 approximants of the primitive icosahedral phase (i phase); (ii) a twice order-induced modulated cubic phase (bcc, a = 25.20 Å) which has been shown to correspond to 1/1 approximant of the ordered i phase [i.e., face-centered icosahedral (FCI)]; and (iii) real crystalline bcc (a = 8.90 Å) and face-centered cubic (fcc) (a = 17.98 Å) phases possessing a specific orientation relationship with the icosahedral matrix phase. Tentative structural models showing the interrelationships between the bcc/fcc phases have been outlined.

scholarly journals Preliminary Analysis on Burnup Calculation of Several Arrangement of TRISO and Pebble inside an MCNP Model of HTR Core

2021 ◽  
Vol 2072 (1) ◽  
pp. 012008
Author(s):  
W Luthfi ◽  
Suwoto ◽  
T Setiadipura ◽  
Zuhair
Keyword(s):  
Reactor Core ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Average Deviation ◽  
Absolute Deviation ◽  
Hexagonal Close Packed ◽  
Simple Cubic ◽  
High Temperature Reactor ◽  
Face Centered ◽  
Burnup Calculation

Abstract Several studies related to simplifying the modeling of pebble bed High-Temperature Reactor core (HTR) has been developed before. From some calculation on several MCNP models with a fueled pebble to dummy ratio 57:43, using a combination of several types of TRISO (TRi-structural ISOtropic particle fuel) unit and Pebble unit is modeled to achieve its first criticality. In this paper, some MCNP model that uses 27000 pebbles with a 57:43 ratio and 100% fueled pebble is created to be used on burnup calculation and to compare its k-eff and nuclide inventory. From this burnup calculation, it could be seen that SC (Simple Cubic) TRISO unit has faster calculation time followed by the HCP (Hexagonal Close Packed) TRISO unit and then the FCC (Face-Centered Cubic) TRISO unit. The BCC (Body-Centered Cubic) pebble unit had some consistent deviation from another pebble unit, and it still needs more study to know more about the reason behind it. It could be seen that if there are some dummy pebbles inside the reactor, then the deviation would be higher than if there is just fueled pebble inside the reactor. On the 57:43 ratio, the absolute average deviation of k-eff on burnup calculation is lower than 2% and 10% for nuclide inventory (mass). On 100% fueled pebble, it’s below 0.15% on k-eff absolute deviation and below 8% on nuclide inventory deviation.

scholarly journals Rectangular Body-centered Cuboid Packing Lattices and Their Possible Applications

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
Xiqiang Zheng
Keyword(s):  
Sphere Packing ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Simple Cubic ◽  
Face Centered ◽  
Packing Method ◽  
Rectangular Body

We first introduce several sphere packing ways such as simple cubic packing (SC), face-centered cubic packing (FCC), body-centered cubic packing (BCC), and rectangular body-centered cuboid packing (recBCC), where the rectangular body-centered cuboid packing means the packing method based on a rectangular cuboid whose base is square and whose height is  times the length of one side of its square base such that the congruent spheres are centered at the 8 vertices and the centroid of the cuboid. The corresponding lattices are denoted as SCL, FCCL, BCCL, and recBCCL, respectively. Then we consider properties of those lattices, and show that FCCL and recBCCL are the same. Finally we point out some possible applications of the recBCC lattices.

Computer simulation of local atomic displacements in alloys. Application to Guinier–Preston zones in Al–Cu

1994 ◽  
Vol 27 (5) ◽  
pp. 772-781 ◽  
Author(s):  
J. Kyobu ◽  
Y. Murata ◽  
M. Morinaga
Keyword(s):  
Short Range ◽  
Structural Models ◽  
Single Layer ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Lattices ◽  
Atomic Displacements ◽  
Cu Alloy ◽  
Combined Use ◽  
Face Centered

A new computer program has been developed for the simulation of local atomic displacements in alloys with face-centered-cubic and body-centered-cubic lattices. The combined use of this program with the Gehlen–Cohen program for the simulation of chemical short-range order completely describes atomic fluctuations in alloys. The method has been applied to the structural simulation of Guinier–Preston (GP) zones in an Al–Cu alloy, using the experimental data of Matsubara & Cohen [Acta Metall. (1985), 33, 1945–1955]. Characteristic displacements of atoms have been observed around the GP zones and new structural models including local displacements have been proposed for a single-layer zone and several multilayer zones.

Sign in / Sign up

Export Citation Format

Share Document