| 1. |
- Bostrom, Mathias, et al.
(författare)
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Lifshitz interaction can promote ice growth at water-silica interfaces
- 2017
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 95:15
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Tidskriftsartikel (refereegranskat)abstract
- At air-water interfaces, the Lifshitz interaction by itself does not promote ice growth. On the contrary, we find that the Lifshitz force promotes the growth of an ice film, up to 1-8 nm thickness, near silica-water interfaces at the triple point of water. This is achieved in a system where the combined effect of the retardation and the zero frequency mode influences the short-range interactions at low temperatures, contrary to common understanding. Cancellation between the positive and negative contributions in the Lifshitz spectral function is reversed in silica with high porosity. Our results provide a model for how water freezes on glass and other surfaces.
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| 2. |
- Gambino, Davide, et al.
(författare)
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Density functional description of spin, lattice, and spin-lattice dynamics in antiferromagnetic and paramagnetic phases at finite temperatures
- 2022
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 106:13
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Tidskriftsartikel (refereegranskat)abstract
- Describing the (a) electronic and magnetic properties (EMPs) of compounds generally requires the specification of (b) the type of spin configurations one is considering [e.g., antiferromagnetic (AFM) or paramagnetic (PM) phases, with or without spin short-range order (SRO)] and lattice structure (e.g., atomic displacements, possible symmetry breaking) of such phases at a given temperature. Indeed, studying the interplay between the spin configuration and lattice structure (SCLS) and the ensuing EMPs has been an outstanding challenge in the theory of matter. The traditional approach of electronic phases of matter has generally focused on the interelectronic interactions, regarding the lattice structure as a spectator degree of freedom (DOF), often fixed from an external source (experiment or model assumptions). However, one expects that the EMPs of a compound can generally respond self-consistently to changes in SCLS (including symmetry), and at the same time, the SCLS can change in response to different electron and spin distributions visited during the calculation of the EMPs. This ping-pong-like interplay where structure affects electronic properties and the latter affect structure is indeed a cornerstone of much of the intricacy of understanding quantum materials. However, there is a limited understanding of the theory required to determine the SCLS at finite temperature in a way that can affect the EMPs and vice versa. We use here a practical, density functional theory (DFT)-based approach that provides the SCLS as a function of temperature, involving the description of spin, lattice, and spin-lattice dynamics of AFM and PM phases, thus providing the required ping-pong partners to the description of the EMPs of different phases. We distinguish three levels of dynamics: (I) dynamics of the spin DOFs treated via noncollinear Heisenberg Monte Carlo solved with exchange energies obtained from first-principles DFT cluster expansion, (II) dynamics of the lattice DOFs treated by ab initio molecular dynamics (AIMD) employing a fixed, representative spin configuration from Level I at the simulated temperature, and (III) coupling of spin and lattice dynamics via Landau-Lifshitz-Gilbert spin dynamics combined with AIMD. Such SCLSs at each of the three levels are used as inputs to DFT supercell calculations, providing the EMPs at each temperature. The results of this sequence include electronic band structures, bandgaps, density of states, as well as the statistical distribution of local moments and the SRO parameters, each as a function of temperature. Herein, we define a path to include temperature in magnetic insulators at different levels of spin dynamics by intercommunication between electronic structure theory and statistical mechanics. Using NiO as a test case, we address the separability of the DOFs in magnetic insulators for a minimal description of EMPs, demonstrating that inclusion of spin dynamics and, to some level, lattice dynamics is enough to explain the EMPs.
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| 3. |
- Kulish, Vadym V., et al.
(författare)
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Adsorption of metal adatoms on single-layer phosphorene
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 17:2, s. 992-1000
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Tidskriftsartikel (refereegranskat)abstract
- Single- or few-layer phosphorene is a novel two-dimensional direct-bandgap nanomaterial. Based on first-principles calculations, we present a systematic study on the binding energy, geometry, magnetic moment and electronic structure of 20 different adatoms adsorbed on phosphorene. The adatoms cover a wide range of valences, including s and p valence metals, 3d transition metals, noble metals, semiconductors, hydrogen and oxygen. We find that adsorbed adatoms produce a rich diversity of structural, electronic and magnetic properties. Our work demonstrates that phosphorene forms strong bonds with all studied adatoms while still preserving its structural integrity. The adsorption energies of adatoms on phosphorene are more than twice higher than on graphene, while the largest distortions of phosphorene are only similar to 0.1-0.2 angstrom. The charge carrier type in phosphorene can be widely tuned by adatom adsorption. The unique combination of high reactivity with good structural stability is very promising for potential applications of phosphorene.
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| 4. |
- Kulish, Vadym V., et al.
(författare)
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Phosphorene as an anode material for Na-ion batteries : a first-principles study
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 17:21, s. 13921-13928
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Tidskriftsartikel (refereegranskat)abstract
- We systematically investigate a novel two-dimensional nanomaterial, phosphorene, as an anode for Na-ion batteries. Using first-principles calculations, we determine the Na adsorption energy, specific capacity and Na diffusion barriers on monolayer phosphorene. We examine the main trends in the electronic structure and mechanical properties as a function of Na concentration. We find a favorable Na-phosphorene interaction with a high theoretical Na storage capacity. We find that Na-phosphorene undergoes semiconductor-metal transition at high Na concentration. Our results show that Na diffusion on phosphorene is fast and anisotropic with an energy barrier of only 0.04 eV. Owing to its high capacity, good stability, excellent electrical conductivity and high Na mobility, monolayer phosphorene is a very promising anode material for Na-ion batteries. The calculated performance in terms of specific capacity and diffusion barriers is compared to other layered 2D electrode materials, such as graphene, MoS2, and polysilane.
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| 5. |
- Li, Yang, et al.
(författare)
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Premelting and formation of ice due to Casimir-Lifshitz interactions : Impact of improved parameterization for materials
- 2022
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 105:1
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the premelting and formation of ice due to the Casimir-Lifshitz interaction, proposed in early 1990s by Elbaum and Schick [Phys. Rev. Lett. 66, 1713 (1991)], have been generalized to diverse practical scenarios, yielding novel physical intuitions and possibilities of application for those phenomena. The properties of materials, in particular, the electrical permittivity and permeability, exert significant influence on the Casimir-Lifshitz energies and forces and hence on the corresponding premelting and formation of ice. To address these influences in detail and explore the resulting physics, here we revisit and extend the analyses of previous work with both the dielectric data utilized there and the latest dielectric functions for ice and cold water. For the four-layer cases considered by some of us, the existence of stable configurations depending on the initial conditions has been confirmed, and different types of stability corresponding to minima of the Casimir-Lifshitz free energy are demonstrated. As the new dielectric functions for ice and cold water deviate considerably from those used by Elbaum and Schick, their vital impact on three- and four-layer configurations is therefore being reconsidered.
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| 6. |
- Malyi, Oleksandr I., et al.
(författare)
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A first principles study of CO2 adsorption on alpha-SiO2(001) surfaces
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 17:31, s. 20125-20133
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Tidskriftsartikel (refereegranskat)abstract
- In this work, using first principles calculations, an analysis of CO2 interaction with cleaved and reconstructed alpha-SiO2(001) surfaces was performed. We showed that CO2 could strongly interact with a cleaved surface forming CO3-like configurations. Here, the binding energy per CO2 molecule depends strongly on CO2 surface coverage and can reach -2.35 eV. Despite this, even with CO2 molecules, the cleaved surface has a substantially higher surface energy than that of the reoptimized "dense'' surface. This observation is also consistent with molecular dynamics simulations. Because of this, for thermodynamically stable system, the interaction of CO2 molecules with a alpha-SiO2(001) surface should be treated as the physisorption of CO2 molecules on the reoptimized "dense'' surface with the binding energy varying from -0.26 eV for single CO2 molecule adsorption to -0.32 eV per molecule for monolayer coverage.
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| 7. |
- Malyi, Oleksandr I., et al.
(författare)
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Energy, Phonon, and Dynamic Stability Criteria of Two-Dimensional Materials
- 2019
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 11:28, s. 24876-24884
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have become a powerful tool to exclude the Edisonian approach in search of novel two-dimensional (2D) materials. However, no universal first-principles criteria to examine the realizability of hypothetical 2D materials have been established in the literature yet. Because of this, and as the calculations are always performed in an artificial simulation environment, one can unintentionally study compounds that do not exist in experiments. Although investigations of physics and chemistry of unrealizable materials can provide some fundamental knowledge, the discussion of their applications can mislead experimentalists for years and increase the gap between experimental and theoretical research. By analyzing energy convex hull, phonon spectra, and structure evolution during ab initio molecular dynamics simulations for a range of synthesized and recently proposed 2D materials, we construct energy, phonon, and dynamic stability filters that need to be satisfied before proposing novel 2D compounds. We demonstrate the power of the suggested filters for several selected 2D systems, revealing that some of them cannot be ever realized experimentally.
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| 8. |
- Malyi, Oleksandr I., et al.
(författare)
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In search of new reconstructions of (001) alpha-quartz surface : a first principles study
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:98, s. 55599-55603
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Tidskriftsartikel (refereegranskat)abstract
- Using Born-Oppenheimer molecular dynamics (BOMD) simulations and "static" density functional theory (DFT) calculations, the stability of cleaved and reconstructed alpha-SiO2(001) surfaces was studied. We found reconstructions ("dense", 2 x 2 reoptimized "dense", and 3 x 3 reoptimized "dense") which minimize the surface energy. The analysis of the surface energies shows that the cleaved surface reconstructs to the 2 x 2 reoptimized "dense" surface having a surface energy around 10% smaller than the "dense" surface. The results suggest that the optimization of Si-Si and Si-O distances at top surface layers plays the key role in stabilizing the 2 x 2 "dense" surface over the well-known "dense" surface.
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| 9. |
- Malyi, Oleksandr, I, et al.
(författare)
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Noble gas as a functional dopant in ZnO
- 2019
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Ingår i: npj Computational Materials. - : SPRINGERNATURE. - 2057-3960. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Owing to fully occupied orbitals, noble gases are considered to be chemically inert and to have limited effect on materials properties under standard conditions. However, using first-principles calculations, we demonstrate herein that the insertion of noble gas (i.e. He, Ne, or Ar) in ZnO results in local destabilization of electron density of the material driven by minimization of an unfavorable overlap of atomic orbitals of the noble gas and its surrounding atoms. Specifically, the noble gas defect (interstitial or substitutional) in ZnO pushes the electron density of its surrounding atoms away from the defect. Simultaneously, the host material confines the electron density of the noble gas. As a consequence, the interaction of He, Ne, or Ar with O vacancies of ZnO in different charge states q (ZnO:V-O(q)) affects the vacancy stability and their electronic structures. Remarkably, we find that the noble gas is a functional dopant that can delocalize the deep in-gap V-O(q) states and lift electrons associated with the vacancy to the conduction band.
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| 10. |
- Malyi, Oleksandr I., et al.
(författare)
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Volume dependence of the dielectric properties of amorphous SiO2
- 2016
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:10, s. 7483-7489
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Tidskriftsartikel (refereegranskat)abstract
- Using first principles calculations, the analysis of the dielectric properties of amorphous SiO2 (am-SiO2) was performed. We found that the am-SiO2 properties are volume dependent, and the dependence is mainly induced by the variation of nanoporosity at the atomic scale. In particular, both ionic and electronic contributions to the static dielectric constants are functions of volume with clear trends. Moreover, using the unique parameterization of the dielectric function provided in this work, we predict dielectric functions at imaginary frequencies of different SiO2 polymorphs having similar band gap energies.
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