Mobility of Self-Interstitials in FCC and BCC Metals

1998 ◽  
Vol 527 ◽  
Author(s):  
Yu.N. Osetsky ◽  
A. Serra ◽  
V. Priego ◽  
F. Gao ◽  
D.J. Bacon
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Diffusion Mechanism ◽  
Three Dimensional ◽  
Stable Configuration ◽  
Interatomic Potentials ◽  
Bcc Metals ◽  
Migration Mechanism ◽  
Different Types ◽  
Diffusion Mechanisms

ABSTRACTDiffusion of self-interstitial atoms (SIAs) has been studied in bcc-Fe and fcc-Cu using molecular dynamics and interatomic potentials of different types. The Fe potentials describe SIA configurations of different stability. The temperature dependence of the SIA diffusion mechanisms is qualitatively similar for both potentials. At high temperature the diffusion is three-dimensional via the <110> dumbbell mechanism. The contribution of one-dimensional mechanism via the <111> crowdion increases when temperature decreases. At low temperature (<300K) the diffusion mechanism depends on the stable configuration of the SIA.In fcc-Cu all the potentials reproduce the same stable configuration, namely the <100> dumbbell. The migration mechanism is mainly a three-dimensional random walk via this dumbbell with small contributions from the <110> crowdion at high temperature and a two-dimensional caging mechanism at low temperature.

scholarly journals GERMINATION AND VIGOUR IN SEEDS OF THE COWPEA IN RESPONSE TO SALT AND HEAT STRESS

2019 ◽  
Vol 32 (1) ◽  
pp. 143-151 ◽  
Author(s):  
Luma Rayane de Lima Nunes ◽  
Paloma Rayane Pinheiro ◽  
Charles Lobo Pinheiro ◽  
Kelly Andressa Peres Lima ◽  
Alek Sandro Dutra
Keyword(s):  
Salt Stress ◽  
Heat Stress ◽  
High Temperature ◽  
Low Temperature ◽  
Vigna Unguiculata ◽  
Salt Concentration ◽  
Dry Weight ◽  
Germination Percentage ◽  
Different Types ◽  
Different Temperatures

ABSTRACT Salinity is prejudicial to plant development, causing different types of damage to species, or even between genotypes of the same species, with the effects being aggravated when combined with other types of stress, such as heat stress. The aim of this study was to evaluate the tolerance of cowpea genotypes (Vigna unguiculata L. Walp.) to salt stress at different temperatures. Seeds of the Pujante, Epace 10 and Marataoã genotypes were placed on paper rolls (Germitest®) moistened with different salt concentrations of 0.0 (control), 1.5, 3.0, 4.5 and 6.0 dS m-1, and placed in a germination chamber (BOD) at temperatures of 20, 25, 30 and 35°C. The experiment was conducted in a completely randomised design, in a 3 × 4 × 5 scheme of subdivided plots, with four replications per treatment. The variables under analysis were germination percentage, first germination count, shoot and root length, and total seedling dry weight. At temperatures of 30 and 35°C, increases in the salt concentration were more damaging to germination in the Epace 10 and Pujante genotypes, while for the Marataoã genotype, damage occurred at the temperature of 20°C. At 25°C, germination and vigour in the genotypes were higher, with the Pujante genotype proving to be more tolerant to salt stress, whereas Epace 10 and Marataoã were more tolerant to high temperatures. Germination in the cowpea genotypes was more sensitive to salt stress when subjected to heat stress caused by the low temperature of 20°C or high temperature of 35°C.

scholarly journals The phase transition of rubidium hydrogen carbonate, RbHCO3

2017 ◽  
Vol 73 (7) ◽  
pp. 975-979 ◽  
Author(s):  
Carla Larvor ◽  
Berthold Stöger
Keyword(s):  
Phase Transition ◽  
Hydrogen Bonding ◽  
High Temperature ◽  
Hydrogen Atom ◽  
Low Temperature ◽  
Three Dimensional ◽  
Disorder Phase Transition ◽  
Dimensional Network ◽  
Hydrogen Carbonate ◽  
Index 2

Rubidium hydrogen carbonate, RbHCO3, features an order/disorder phase transition atTC= 245 K from the high-temperature (HT) disorderedC2/mmodification to the low-temperature (LT)C-1 modification. The crystal structures are characterized by [HCO3]22−pairs of hydrogen carbonate groups connected by strong hydrogen bonding. The [HCO3]22−pairs are connected by Rb+cations into a three-dimensional network. In HT-RbHCO3, the hydrogen atom is disordered. In LT-RbHCO3, ordering of the hydrogen atom leads to atranslationengleichesymmetry reduction of index 2. The lost reflections and rotations are retained as twin operations.

scholarly journals Construction of an n-Body Potential for Revealing the Atomic Mechanism for Direct Alloying of Immiscible Tungsten and Copper

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 5988
Author(s):  
Tao Zeng ◽  
Fei Li ◽  
Yuan Huang
Keyword(s):  
High Temperature ◽  
Interatomic Potential ◽  
Diffusion Mechanism ◽  
Critical Role ◽  
Experimental Studies ◽  
Md Simulations ◽  
Interatomic Potentials ◽  
Direct Alloying ◽  
Materials Used ◽  
Body Potential

W-Cu laminated composites are critical materials used to construct nuclear fusion reactors, and it is very important to obtain direct alloying between W and Cu at the W/Cu interfaces of the composites. Our previous experimental studies showed that it is possible to overcome the immiscibility between W and Cu and obtain direct alloying when the alloying temperature is close to the melting point of Cu. Because the W-Cu interatomic potentials published thus far cannot accurately reproduce the alloying behaviors of immiscible W and Cu, an interatomic potential suitable for the W-Cu system has been constructed in the present study. Based on this potential, direct alloying between W and Cu at high temperature has been verified, and the corresponding diffusion mechanism has been studied, through molecular dynamics (MD) simulations. The results indicate that the formation of an amorphous Cu layer at the W/Cu interface plays a critical role in alloying because it allows Cu atoms to diffuse into W. The simulation results for direct alloying between W and Cu can be verified by experimental results and transmission electron microscopy observations. This indicates that the constructed W-Cu potential can correctly model the high-temperature performance of the W-Cu system and the diffusion mechanism of direct alloying between W and Cu.

scholarly journals Comparison of the crystal structures of the low- and high-temperature forms of bis[4-(dimethylamino)pyridine]dithiocyanatocobalt(II)

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Christoph Krebs ◽  
Inke Jess ◽  
Christian Näther
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Three Dimensional ◽  
Monoclinic Space Group ◽  
Temperature Form ◽  
Dimensional Network ◽  
High Temperature Form

Single crystals of the high-temperature form I of [Co(NCS)2(DMAP)2] (DMAP = 4-dimethylaminopyridine, C7H10N2) were obtained accidentally by the reaction of Co(NCS)2 with DMAP at slightly elevated temperatures under kinetic control. This modification crystallizes in the monoclinic space group P21/m and is isotypic with the corresponding Zn compound. The asymmetric unit consists of one crystallographically independent Co cation and two crystallographically independent thiocyanate anions that are located on a crystallographic mirror plane and one DMAP ligand (general position). In its crystal structure the discrete complexes are linked by C—H...S hydrogen bonds into a three-dimensional network. For comparison, the crystal structure of the known low-temperature form II, which is already thermodynamically stable at room temperature, was redetermined at the same temperature. In this polymorph the complexes are connected by C—H...S and C—H...N hydrogen bonds into a three-dimensional network. At 100 K the density of the high-temperature form I (ρ = 1.457 g cm−3) is lower than that of the low-temperature form II (ρ = 1.462 g cm−3), which is in contrast to the values determined by XRPD at room temperature. Therefore, these two forms represent an exception to the Kitaigorodskii density rule, for which extensive intermolecular hydrogen bonding in form II might be responsible.

Industrialization of tailoring spherical cathode material towards high-capacity, cycling-stable and superior low temperature performance for lithium-ion batteries

RSC Advances ◽  
2016 ◽  
Vol 6 (100) ◽  
pp. 97818-97824 ◽  
Author(s):  
Zhonghui Sun ◽  
Liansheng Jiao ◽  
Yingying Fan ◽  
Fenghua Li ◽  
Dandan Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Cathode Material ◽  
Lithium Ion Batteries ◽  
High Capacity ◽  
Lithium Ion ◽  
Precipitation Method ◽  
Temperature Performance ◽  
Different Types ◽  
Co Precipitation

Three different types of spherical cathodes (Li[Ni0.6Co0.2Mn0.2]O2) were synthesized via hydroxide co-precipitation method coupled with high temperature lithiation process.

COEXISTENCE OF DIFFERENT TYPES OF TRANSVERSE CONDUCTIVITY IN Y1-xPrxBa2Cu3 O7-δ SINGLE CRYSTALS WITH DIFFERENT PRASEODYMIUM CONCENTRATIONS

2013 ◽  
Vol 27 (27) ◽  
pp. 1350198 ◽  
Author(s):  
R. V. VOVK ◽  
N. R. VOVK ◽  
I. L. GOULATIS ◽  
A. CHRONEOS
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Single Crystals ◽  
Insulator Transition ◽  
Superconducting Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Different Types ◽  
Transverse Conductivity ◽  
Praseodymium Doping

In this paper, the influence of praseodymium doping on the conductivity across (transverse) the basal plane of high-temperature superconducting Y 1-x Pr x Ba 2 Cu 3 O 7-δ single crystals is investigated. It is determined that an increase of praseodymium doping leads to increased localization effects and the implementation of a metal–insulator transition Y 1-x Pr x Ba 2 Cu 3 O 7-δ, which always precedes the superconducting transition. The increase of the praseodymium concentration also leads to a significant displacement of the point of the metal–insulator transition to the low temperature region.

Water Temperature Modeling and Water Temperature Stratification Pattern of Reservoir Based on the Three-Dimensional Environment Fluid Dynamics Code Model

2014 ◽  
Vol 1073-1076 ◽  
pp. 2321-2326 ◽  
Author(s):  
Fen Fen Yan ◽  
Long Xi Han ◽  
Rong Xu Chen ◽  
Lin Zhang ◽  
Qi Liang Chen
Keyword(s):  
Fluid Dynamics ◽  
High Temperature ◽  
Low Temperature ◽  
Water Temperature ◽  
Three Dimensional ◽  
Temperature Stratification ◽  
Ecological Environment ◽  
Reservoir Water ◽  
Code Model ◽  
Temperature Water

The three-dimensional flow-temperature numerical coupling model was established based on the Three-Dimensional Environment Fluid Dynamics Code Model. The reservoir water temperature was simulated coupled flow and water temperature and stratification pattern was analyzed attempting to provide scientific reference for water design and operation management on proposed reservoir, which could slow down the influence of low temperature water of proposed reservoir on ecological environment and aquatic biodiversity of the downstream river. Results show that reservoir water temperature stratification pattern distinguishes obviously among low temperature period, rising temperature period, high temperature period and cooling period and the temperature hysteresis effect is remarkable. The drainage of low-temperature water in summer should be prevented from influencing downstream ecological environment and the mechanism of the impact of high-temperature water in winter on ecological environment needs further study.

Synthesis and Thermoelectric Properties of NaxCo2O4 Single Crystals

2005 ◽  
Vol 886 ◽  
Author(s):  
Jian He ◽  
Kelvin Aaron ◽  
Edward Abbott ◽  
Joseph Kolis ◽  
Terry M. Tritt
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Low Temperature ◽  
Single Crystal ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Free Path ◽  
Mean Free Path ◽  
Flux Method ◽  
Different Types

ABSTRACTSingle crystal NaCo2O4 platelets with sizes up to 6mm were synthesized by the typical high temperature NaCl flux method. The in-plane thermopower α and in-plane resistivity ρ were measured to be ∼100µV/K and 0.3mΩ-cm at 300K, respectively. The in-plane thermal conductivity κ was measured by our custom-designed “PTC” system and found to be ∼5 W-m−1K−1 at 300K, which is 2-3 times larger than the polycrystalline NaCo2O4. The in-plane phonon mean free path lph was estimated to be ∼9.5Å, which is much smaller than the in-plane mean free path of conducting carriers (la∼51Å). A novel low temperature flux method where NaCl/NaOH was used as flux and metallic Co powders as Co source was developed to successfully synthesize Na-deficient NaxCo2O4 crystals with size up to 6mm at low temperature of 550°C. The different temperature dependence in resistivity reveals that two different types of crystals can exist, one is metallic and another is semiconducting. The temperature dependence of the measured k is like that of a disordered solid and the value is found to be ∼7 W-m−1K−1 at 300K.

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