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Corso, Alessandro Dal; Olsen, Martin; Steenstrup, Kasper Hornbak; Wilm, Jakob; Jensen, Sebastian Hoppe Nesgaard; Paulsen, Rasmus Reinhold; Eiríksson, Eyþór Rúnar; Nielsen, Jakob Skov; Frisvad, Jeppe Revall; Einarsson, Guðmundur; Kjer, Hans Martin

doi:10.1145/2820926.2820950

Cited by 11 publications

(6 citation statements)

References 5 publications

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“…Density-functional theory calculations have been performed with the Quantum-ESPRESSO distribution [45], using the local-density approximation and normconserving pseudopotentials from the PSLibrary [53]; for graphene a plane-wave cutoff of 90 Ry and a Methfessel-Paxton smearing of 0.02 Ry have been used and for silicon a plane-wave cutoff of 100 Ry. Graphene is simulated with a slab geometry, using an optimized lattice parameter a = 4.607 Bohr and a cell height c = 3a; for silicon we find an optimized lattice parameter of 10.18 Bohr.…”

Section: First-principles Simulationsmentioning

confidence: 99%

Thermal Transport in Crystals as a Kinetic Theory of Relaxons

2016

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Thermal conductivity in dielectric crystals is the result of the relaxation of lattice vibrations described by the phonon Boltzmann transport equation. Remarkably, an exact microscopic definition of the heat carriers and their relaxation times is still missing: phonons, typically regarded as the relevant excitations for thermal transport, cannot be identified as the heat carriers when most scattering events conserve momentum and do not dissipate heat flux. This is the case for twodimensional or layered materials at room temperature, or three-dimensional crystals at cryogenic temperatures. In this work we show that the eigenvectors of the scattering matrix in the Boltzmann equation define collective phonon excitations, termed here relaxons. These excitations have well defined relaxation times, directly related to heat flux dissipation, and provide an exact description of thermal transport as a kinetic theory of the relaxon gas. We show why Matthiessen's rule is violated, and construct a procedure for obtaining the mean free paths and relaxation times of the relaxons. These considerations are general, and would apply also to other semiclassical transport models, such as the electronic Boltzmann equation. For heat transport, they remain relevant even in conventional crystals like silicon, but are of the utmost importance in the case of two-dimensional materials, where they can revise by several orders of magnitude the relevant time-and length-scales for thermal transport in the hydrodynamic regime. arXiv:1603.02608v3 [cond-mat.mtrl-sci]

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Section: First-principles Simulationsmentioning

confidence: 99%

Thermal Transport in Crystals as a Kinetic Theory of Relaxons

2016

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“…The functional employed was PBEsol, [23] which was shown to yield reasonable NMR chemical shifts in hydrated AlPO 4 -34, [14] accurately reproducing the experimental structure. Pseudopotentials were from PSLibrary, [24,25] version 1.0.0. The library provides two types of pseudopotentials for certain elements with different speed/accuracy tradeoffs; the more accurate versions were used, requiring 90 and 360 Ry plane-wave energy cutoffs for wavefunctions and densities, respectively, to achieve good force and stress convergence.…”

Section: Methodsmentioning

confidence: 99%

Superior Performance of Microporous Aluminophosphate with LTA Topology in Solar‐Energy Storage and Heat Reallocation

Krajnc

Varlec

Mazaj

et al. 2017

Advanced Energy Materials

109

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Hydrophilic porous materials are recognized as very promising materials for water-sorption-based energy storage and transformation. In this study, a porous, zeolite-like aluminophosphate with LTA (Linde Type A) topology is inspected as an energy-storage material. The study is motivated by the material's high predicted pore volume. According to sorption and calorimetric tests, the aluminophosphate outperforms all other zeolite-like and metal-organic porous materials tested so far. It adsorbs water in an extremely narrow relative-pressure interval (0.10 < p/p 0 < 0.15) and exhibits superior water uptake (0.42 g g −1 ) and energy-storage capacity (527 kW h m −3 ). It also shows remarkable cycling stability; after 40 cycles of adsorption/desorption its capacity drops by less than 2%. Desorption temperature for this material, which is one of crucial parameters in applications, is lower from desorption temperatures of other tested materials by 10-15 °C. Furthermore, its heatpump performance is very high, allowing efficient cooling in demanding conditions (with cooling power up to 350 kW h m −3 even at 30 °C temperature difference between evaporator and environment). On the microscopic scale, sorption mechanism in AlPO 4 -LTA is elucidated by X-ray diffraction, nuclear magnetic resonance measurements, and first-principles calculations. In this aluminophosphate, energy is stored predominately in hydrogen-bonded network of water molecules within the pores.

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“…1. thermo pw: Thermal properties from the quasi-harmonic approximation thermo pw [31] is a collection of codes aimed at computing various thermodynamical quantities in the quasi-harmonic approximation. The key ingredient is the vibrational contribution, F ph , to the Helmholtz free energy at temperature T :…”

Section: Other Lattice-dynamical and Thermal Propertiesmentioning

confidence: 99%

“…• thermo pw, for computing thermodynamical properties in the quasi-harmonic approximation, also featuring an advanced master-slave distributed computing scheme, applicable to generic high-throughput calculations [31].…”

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confidence: 99%

“…Complementary to this, a complete pseudopotential library, pslibrary, including fullyrelativistic pseudopotentials, has been generated [36,37]. A curation effort [38] on all the pseudopotential libraries available for Quantum ESPRESSO has led to the identification of optimal pseudopotentials for efficiency or for accuracy in the calculations, the latter delivering an agreement comparable to any of the best all-electron codes [5].…”

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confidence: 99%

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Advanced capabilities for materials modelling with Quantum ESPRESSO

Giannozzi

Andreussi

Brumme

et al. 2017

J. Phys.: Condens. Matter

6,232

3,835

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Quantum ESPRESSO is an integrated suite of open-source computer codes for quantum simulations of materials using state-of-the art electronic-structure techniques, based on density-functional theory, density-functional perturbation theory, and many-body perturbation theory, within the plane-wave pseudo-potential and projector-augmented-wave approaches. Quantum ESPRESSO owes its popularity to the wide variety of properties and processes it allows to simulate, to its performance on an increasingly broad array of hardware architectures, and to a community of researchers that rely on its capabilities as a core open-source development platform to implement theirs ideas. In this paper we describe recent extensions and improvements, covering new methodologies and property calculators, improved parallelization, code modularization, and extended interoperability both within the distribution and with external software.

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VirtualTable

Cited by 11 publications

References 5 publications

Thermal Transport in Crystals as a Kinetic Theory of Relaxons

Thermal Transport in Crystals as a Kinetic Theory of Relaxons

Superior Performance of Microporous Aluminophosphate with LTA Topology in Solar‐Energy Storage and Heat Reallocation

Advanced capabilities for materials modelling with Quantum ESPRESSO

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