| 1. |
- Mun, Seungsoo, et al.
(author)
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Reconfigurable dual-mode optical encryption enabled by block copolymer photonic crystal with micro-imprinted holographic metasurface
- 2023
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In: Materials Today. - : ELSEVIER SCI LTD. - 1369-7021 .- 1873-4103. ; 70, s. 44-56
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Journal article (peer-reviewed)abstract
- Dual-mode optical encryption based on holographic metasurfaces and color components is of great attraction because of their enhanced information security and storage; however, the realization of independently as well as reversibly encodable holographic metasurfaces and color components remains unreported. Herein, we present reconfigurable dual-mode encryptions of structural colors (SC) and holograms, achieved through stimuli-responsive block copolymer (BCP) photonic crystals (PCs) with micro-imprinted holographic metasurfaces. Holographic images appear when the micro-imprinted BCP PCs, consisting of self-assembled alternating lamellae of two dielectrics, are exposed to an incident laser. A characteristic SC develops in the visible range when the imprinted film is immersed in a liquid agent that can swell one of the dielectrics, allowing for dual-mode holographic and SC encodings in the solid and liquid states, respectively. The dual-mode optical encoding is reconfigured. The holographic image can be erased and replaced with another micropattern, while preserving the SC. Moreover, an SC, set by crosslinking of the swellable lamellae, is reset by chemical de-crosslinking and subsequent transient re-crosslinking, enabling the SC reconfigurability of the BCP PC film. A prototype of a high-security reconfigurable dual encryption has been developed, wherein true information is decrypted when holographic passwords are confirmed with full-color visible SC passwords.
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| 2. |
- Berland, Kristian, 1983, et al.
(author)
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van der Waals density functionals built upon the electron-gas tradition: Facing the challenge of competing interactions
- 2014
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In: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 140:18, s. 18A539 -
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Journal article (peer-reviewed)abstract
- The theoretical description of sparse matter attracts much interest, in particular for those ground-state properties that can be described by density functional theory. One proposed approach, the van der Waals density functional (vdW-DF) method, rests on strong physical foundations and offers simple yet accurate and robust functionals. A very recent functional within this method called vdW-DF-cx [K. Berland and P. Hyldgaard, Phys. Rev. B89, 035412 (2014)] stands out in its attempt to use an exchange energy derived from the same plasmon-based theory from which the nonlocal correlation energy was derived. Encouraged by its good performance for solids, layered materials, and aromatic molecules, we apply it to several systems that are characterized by competing interactions. These include the ferroelectric response in PbTiO3, the adsorption of small molecules within metal-organic frameworks, the graphite/diamond phase transition, and the adsorption of an aromatic-molecule on the Ag(111) surface. Our results indicate that vdW-DF-cx is overall well suited to tackle these challenging systems. In addition to being a competitive density functional for sparse matter, the vdW-DF-cx construction presents a more robust general-purpose functional that could be applied to a range of materials problems with a variety of competing interactions.
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| 3. |
- Berland, Kristian, 1983, et al.
(author)
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van der Waals forces in density functional theory: a review of the vdW-DF method
- 2015
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In: Reports on Progress in Physics. - : IOP Publishing. - 0034-4885 .- 1361-6633. ; 78:6, s. 066501-
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Journal article (peer-reviewed)abstract
- A density functional theory (DFT) that accounts for van der Waals (vdW) interactions incondensed matter, materials physics, chemistry, and biology is reviewed. The insights that ledto the construction of the Rutgers–Chalmers van der Waals density functional (vdW-DF) arepresented with the aim of giving a historical perspective, while also emphasizing more recentefforts which have sought to improve its accuracy. In addition to technical details, we discussa range of recent applications that illustrate the necessity of including dispersion interactionsin DFT. This review highlights the value of the vdW-DF method as a general-purpose method,not only for dispersion bound systems, but also in densely packed systems where these typesof interactions are traditionally thought to be negligible.
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| 4. |
- Lee, Kyuho, et al.
(author)
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Benchmarking van der Waals density functionals with experimental data: potential-energy curves for H2 molecules on Cu(111), (100) and (110) surfaces
- 2012
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In: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:42
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Journal article (peer-reviewed)abstract
- Detailed physisorption data from experiment for the H2 molecule on low-index Cu surfaces challenge theory. Recently, density functional theory (DFT) has been developed to account for nonlocal correlation effects, including van der Waals (dispersion) forces. We show that the functional vdW-DF2 gives a potential-energy curve, potential-well energy levels and difference in lateral corrugation promisingly close to the results obtained by resonant elastic backscattering–diffraction experiments. The backscattering barrier is sensitive to the choice of exchange functional approximation. Further, the DFT-D3 and TS-vdW corrections to traditional DFT formulations are also benchmarked, and deviations are analyzed.
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| 5. |
- Rangel, Tonatiuh, et al.
(author)
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Structural and excited-state properties of oligoacene crystals from first principles
- 2016
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In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 93
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Journal article (peer-reviewed)abstract
- Molecular crystals are a prototypical class of van der Waals (vdW) bound organic materials with excited state properties relevant for optoelectronic applications. Predicting the structure and excited state properties of molecular crystals presents a challenge for electronic structure theory, as standard approximations to density functional theory (DFT) does not cover the long ranged vdW dispersion interactions and do not yield excited state properties. In this work we use a a combination of DFT including vdW forces -- using both nonlocal functionals and pair-wise correction methods -- together with many-body perturbation theory (MBPT) to study the geometry and excited states, respectively, of the entire set of oligoacene crystals, from benzene to hexazene. We find that vdW methods can predict lattice constants within 1 percent of the experimental measurements, on par with the previously reported accuracy of the pair-wise approximations for the same systems. We further find that the excitations energies are sensitive to the geometry, but if optimized geometries are used MBPT can yield excited state properties within a few tenths of an eV from experiments. We elucidate trends in MBPT-charge and neutral excitation energies across the acene series and discuss the role of common approximations used in MBPT.
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