Multiscale Approach to Theoretical Simulations of Materials for Nuclear Energy Applications: Fe-Cr and Zr-based Alloys

2013 ◽  
Vol 1514 ◽  
pp. 3-14
Author(s):  
Igor A. Abrikosov ◽  
Alena V. Ponomareva ◽  
Svetlana A. Barannikova ◽  
Olle Hellman ◽  
Olga Yu. Vekilova ◽  
...  
Keyword(s):  
First Principles ◽  
Nuclear Energy ◽  
Ferromagnetic State ◽  
Mixing Enthalpy ◽  
Multiscale Approach ◽  
Efficient Treatment ◽  
Energy Applications ◽  
Novel Approach ◽  
Cr Concentration ◽  
Theoretical Simulations

ABSTRACTWe review basic ideas behind state-of-the-art techniques for first-principles theoretical simulations of the phase stabilities and properties of alloys. We concentrate on methods that allow for an efficient treatment of compositional and thermal disorder effects. In particular, we present novel approach to evaluate free energy for strongly anharmonic systems. Theoretical tools are then employed in studies of two materials systems relevant for nuclear energy applications: Fe-Cr and Zr-based alloys. In particular, we investigate the effect of hydrostatic pressure and multicomponent alloying on the mixing enthalpy of Fe-Cr alloys, and show that in the ferromagnetic state both of them reduce the alloy stability at low Cr concentration. For Zr-Nb alloys, we demonstrate how microscopic parameters calculated from first-principles can be used in higher-level models.

First-principles modeling of materials for nuclear energy applications

2014 ◽  
Author(s):  
Andrey I. Dmitriev ◽  
Alena V. Ponomareva ◽  
Anton Yu. Nikonov ◽  
Igor A. Abrikosov ◽  
Svetlana A. Barannikova
Keyword(s):  
First Principles ◽  
Nuclear Energy ◽  
Energy Applications

First-Principles Theory of Polarization in Ferroelectrics

1992 ◽  
Vol 291 ◽  
Author(s):  
R. Resta ◽  
M. Posternak ◽  
A. Baldereschi
Keyword(s):  
Spontaneous Polarization ◽  
First Principles ◽  
Ferroelectric Materials ◽  
Recent Experimental Data ◽  
Modern Theory ◽  
Rigid Core ◽  
Novel Approach ◽  
Prototype Structure ◽  
Effective Charges ◽  
The Difference

ABSTRACTWe outline a modern theory of the spontaneous polarization P in pyroelectric and ferroelectric materials. Although P itself isnot an observable, the difference ΔP between two crystal states can indeed be measured and calculated. We define P as the difference between the polar structure and a suitably chosen nonpolar prototype structure. We previously proposed and implemented a supercell scheme in order to evaluate P in pyroelectric BeO; here we adopt an approach recently developed by King-Smith and Vanderbilt, where ΔP is obtained from the computation of Berry's phases, with no use of supercells. We apply this novel approach, which is numerically very convenient, in order to revisit our previous work on BeO. We then perform a first-principles investigation of the spontaneous polarization P of KNbO3 in its tetragonal phase, which is a well studied perovskite ferroelectric. Our calculated P value confirms the most recent experimental data. The polarization is linear in the ferroelectric distortion; the Born effective charges show strong variations from nominal ionic values, and a large inequivalence of the 0 ions. Only the highest nine valence-band states (O 2p) contribute to P, while all the other states behave as rigid core states.

First-Principles Investigation of Two-Dimensional Covalent Organic Frameworks Electrocatalysts for Oxygen Evolution/Reduction and Hydrogen Evolution Reactions

2021 ◽  
Author(s):  
Jing Ji ◽  
Cunjin Zhang ◽  
Shuaibo Qin ◽  
Peng Jin
Keyword(s):  
Renewable Energy ◽  
Hydrogen Evolution ◽  
Oxygen Evolution ◽  
Hydrogen Evolution Reaction ◽  
First Principles ◽  
Oxygen Evolution Reaction ◽  
Reduction Reaction ◽  
Two Dimensional ◽  
Energy Applications ◽  
Hydrogen Evolution Reactions

The oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) all have attracted much attention due to their utmost importance for clean and renewable energy applications....

First-Principles Studies of the Magnetic Properties of hcp Cr in Cr/Cu(111) and Cr/Ru(0001) Superlattices

2002 ◽  
Vol 721 ◽  
Author(s):  
G. Y. Guo
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Recent Observation ◽  
Theoretical Calculations ◽  
Ferromagnetic State ◽  
Full Potential ◽  
Generalized Gradient ◽  
Plane Wave Method ◽  
Wide Range ◽  
Linearized Augmented Plane Wave

AbstractLatest first-principles density functional theoretical calculations using the generalized gradient approximation and highly accurate all-eleectron full-potential linearized augmented plane wave method, show that bulk hcp Cr would be a paramagnet and that no ferromagnetic state could be stabilized over a wide range of volume [1]. To understand the recent observation of the weakly ferromagnetic state of Cr in hcp Cr/Ru (0001) superlattices [2], the same theoretical calculations have been carried out for the hcp Cr3/Ru7 (0001) and hcp Cr3/fcc Cu6 (111) superlattices. The Cr/Ru superlattice is found to be ferromagnetic with a small magnetic moment of ∼0.31μB/Cr while in contrast, Cr/Cu superlattice is found to be nonmagnetic.

scholarly journals Optimisation of confinement in a fusion reactor using a nonlinear turbulence model

2018 ◽  
Vol 84 (2) ◽  
Author(s):  
E. G. Highcock ◽  
N. R. Mandell ◽  
M. Barnes ◽  
W. Dorland
Keyword(s):  
First Principles ◽  
Figure Of Merit ◽  
Large Scale ◽  
Unit Volume ◽  
Fusion Reactor ◽  
Small Scale ◽  
Zonal Flows ◽  
Novel Approach ◽  
First Time ◽  
Turbulent Cascade

The confinement of heat in the core of a magnetic fusion reactor is optimised using a multidimensional optimisation algorithm. For the first time in such a study, the loss of heat due to turbulence is modelled at every stage using first-principles nonlinear simulations which accurately capture the turbulent cascade and large-scale zonal flows. The simulations utilise a novel approach, with gyrofluid treatment of the small-scale drift waves and gyrokinetic treatment of the large-scale zonal flows. A simple near-circular equilibrium with standard parameters is chosen as the initial condition. The figure of merit, fusion power per unit volume, is calculated, and then two control parameters, the elongation and triangularity of the outer flux surface, are varied, with the algorithm seeking to optimise the chosen figure of merit. A twofold increase in the plasma power per unit volume is achieved by moving to higher elongation and strongly negative triangularity.

scholarly journals Multiscale modelling for tokamak pedestals

2018 ◽  
Vol 84 (2) ◽  
Author(s):  
I. G. Abel ◽  
A. Hallenbert
Keyword(s):  
First Principles ◽  
Detailed Comparison ◽  
Multiscale Approach ◽  
Systems Of Equations ◽  
Line Region ◽  
Open Field Line ◽  
Small Parameters ◽  
The Relationship ◽  
Kinetic Physics ◽  
Current Modelling

Pedestal modelling is crucial to predict the performance of future fusion devices. Current modelling efforts suffer either from a lack of kinetic physics, or an excess of computational complexity. To ameliorate these problems, we take a first-principles multiscale approach to the pedestal. We will present three separate sets of equations, covering the dynamics of edge localised modes (ELMs), the inter-ELM pedestal and pedestal turbulence, respectively. Precisely how these equations should be coupled to each other is covered in detail. This framework is completely self-consistent; it is derived from first principles by means of an asymptotic expansion of the fundamental Vlasov–Landau–Maxwell system in appropriate small parameters. The derivation exploits the narrowness of the pedestal region, the smallness of the thermal gyroradius and the low plasma$\unicode[STIX]{x1D6FD}$(the ratio of thermal to magnetic pressures) typical of current pedestal operation to achieve its simplifications. The relationship between this framework and gyrokinetics is analysed, and possibilities to directly match our systems of equations onto multiscale gyrokinetics are explored. A detailed comparison between our model and other models in the literature is performed. Finally, the potential for matching this framework onto an open-field-line region is briefly discussed.

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