Disordered hyperuniformity in two-dimensional amorphous silica

Disordered hyperuniformity (DHU) is a recently proposed new state of matter, which has been observed in a variety of classical and quantum many-body systems. DHU systems are characterized by vanishing infinite-wavelength normalized density fluctuations and are endowed with unique novel physical properties. Here, we report the discovery of disordered hyperuniformity in atomic-scale two-dimensional materials, i.e., amorphous silica composed of a single layer of atoms, based on spectral-density analysis of high-resolution transmission electron microscopy images. Moreover, we show via large-scale density functional theory calculations that DHU leads to almost complete closure of the electronic bandgap compared to the crystalline counterpart, making the material effectively a metal. This is in contrast to the conventional wisdom that disorder generally diminishes electronic transport and is due to the unique electron wave localization induced by the topological defects in the DHU state.

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Strain and electric field tunable electronic structure of buckled bismuthene

RSC Advances ◽

10.1039/c7ra05787c ◽

2017 ◽

Vol 7 (63) ◽

pp. 39546-39555 ◽

Cited By ~ 31

Author(s):

Ming-Yang Liu ◽

Yang Huang ◽

Qing-Yuan Chen ◽

Ze-Yu Li ◽

Chao Cao ◽

...

Keyword(s):

Density Functional Theory ◽

Electronic Structure ◽

Electric Field ◽

First Principles ◽

Density Functional ◽

Single Layer ◽

Density Functional Theory Calculations ◽

Two Dimensional ◽

Functional Theory

Based on first-principles density functional theory calculations, we systemically study the properties of two-dimensional buckled single-layer bismuth (b-bismuthene).

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Tensor-structured algorithm for reduced-order scaling large-scale Kohn–Sham density functional theory calculations

npj Computational Materials ◽

10.1038/s41524-021-00517-5 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Chih-Chuen Lin ◽

Phani Motamarri ◽

Vikram Gavini

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Large Scale ◽

Density Functional Theory Calculations ◽

System Size ◽

Real Space ◽

Functional Theory ◽

Reduced Order ◽

Separable Approximation ◽

Tensor Basis

AbstractWe present a tensor-structured algorithm for efficient large-scale density functional theory (DFT) calculations by constructing a Tucker tensor basis that is adapted to the Kohn–Sham Hamiltonian and localized in real-space. The proposed approach uses an additive separable approximation to the Kohn–Sham Hamiltonian and an L1 localization technique to generate the 1-D localized functions that constitute the Tucker tensor basis. Numerical results show that the resulting Tucker tensor basis exhibits exponential convergence in the ground-state energy with increasing Tucker rank. Further, the proposed tensor-structured algorithm demonstrated sub-quadratic scaling with system-size for both systems with and without a gap, and involving many thousands of atoms. This reduced-order scaling has also resulted in the proposed approach outperforming plane-wave DFT implementation for systems beyond 2000 electrons.

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Ab Initio Calculation of Mechanical Properties of Stacking Fault in 3C-SiC: Effect of Stress and Doping

Materials Science Forum ◽

10.4028/www.scientific.net/msf.717-720.415 ◽

2012 ◽

Vol 717-720 ◽

pp. 415-418

Author(s):

Yoshitaka Umeno ◽

Kuniaki Yagi ◽

Hiroyuki Nagasawa

Keyword(s):

Mechanical Properties ◽

Ab Initio ◽

Density Functional ◽

Stacking Faults ◽

Single Layer ◽

Local Strain ◽

Density Functional Theory Calculations ◽

Stacking Fault ◽

Functional Theory ◽

N Doping

We carry out ab initio density functional theory calculations to investigate the fundamental mechanical properties of stacking faults in 3C-SiC, including the effect of stress and doping atoms (substitution of C by N or Si). Stress induced by stacking fault (SF) formation is quantitatively evaluated. Extrinsic SFs containing double and triple SiC layers are found to be slightly more stable than the single-layer extrinsic SF, supporting experimental observation. Effect of tensile or compressive stress on SF energies is found to be marginal. Neglecting the effect of local strain induced by doping, N doping around an SF obviously increase the SF formation energy, while SFs seem to be easily formed in Si-rich SiC.

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Nanoribbons with Non-Alternant Topology from Fusion of Polyazulene: Carbon Allotropes Beyond Graphene

10.26434/chemrxiv.9247694.v1 ◽

2019 ◽

Author(s):

Qitang Fan ◽

Daniel Martin-Jimenez ◽

Daniel Ebeling ◽

Claudio K. Krug ◽

Lea Brechmann ◽

...

Keyword(s):

Density Functional Theory ◽

Low Temperature ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Scanning Probe ◽

Two Dimensional ◽

Reaction Step ◽

Functional Theory ◽

Carbon Allotropes ◽

Temperature Scanning

Various two-dimensional (2D) carbon allotropes with non-alternant topologies, such as pentaheptites and phagraphene, have been proposed. Predictions indicate that these metastable carbon polymorphs, which contain odd-numbered rings, possess unusual (opto)electronic properties. However, none of these materials has been achieved experimentally due to synthetic challenges. In this work, by using on-surface synthesis, nanoribbons of the non-alternant graphene allotropes, phagraphene and tetra-penta-hepta(TPH)-graphene have been obtained by dehydrogenative C-C coupling of 2,6-polyazulene chains. These chains were formed in a preceding reaction step via on-surface Ullmann coupling of 2,6-dibromoazulene. Low-temperature scanning probe microscopies with CO-functionalized tip and density functional theory calculations have been used to elucidate their structural properties. <br>

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Aluminum Doping Effect on Surface Structure of Silver Ultrathin Films

Materials ◽

10.3390/ma15020648 ◽

2022 ◽

Vol 15 (2) ◽

pp. 648

Author(s):

Han Yan ◽

Xiong Xu ◽

Peng Li ◽

Peijie He ◽

Qing Peng ◽

...

Keyword(s):

Density Functional ◽

Near Infrared ◽

Single Layer ◽

Density Functional Theory Calculations ◽

Light Transmittance ◽

Formation Mechanisms ◽

Silver Surface ◽

Silver Films ◽

Migration Pathway ◽

Surface Morphologies

Ultrathin silver films with low loss in the visible and near-infrared spectrum range have been widely used in the fields of metamaterials and optoelectronics. In this study, Al-doped silver films were prepared by the magnetron sputtering method and were characterized by surface morphology, electrical conductivity, and light transmittance analyses. Molecular dynamics simulations and first-principles density functional theory calculations were applied to study the surface morphologies and migration pathway for the formation mechanisms in Al-doped silver films. The results indicate that the migration barrier of silver on a pristine silver surface is commonly lower than that of an Al-doped surface, revealing that the aluminum atoms in the doping site decrease the surface mobility and are conducive to the formation of small islands of silver. When the islands are dense, they coalesce into a single layer, leading to a smoother surface. This might be the reason for the observably lower 3D growth mode of silver on an Al-doped silver surface. Our results with electronic structure insights on the mechanism of the Al dopants on surface morphologies might benefit the quality control of the silver thin films.

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Mechanochemical Synthesis of a Mercury(II) Metal-Organic Framework Reveals a Two-Dimensional Polymorph Stabilized by Weak Interactions

10.26434/chemrxiv.9725303.v1 ◽

2019 ◽

Author(s):

Isaiah R. Speight ◽

Igor Huskić ◽

Mihails Arhangelskis ◽

Hatem M. Titi ◽

Robin Stein ◽

...

Keyword(s):

Density Functional ◽

Weak Interactions ◽

Metal Organic Framework ◽

Three Dimensional ◽

Density Functional Theory Calculations ◽

Dimensional Structure ◽

Reaction Monitoring ◽

Two Dimensional ◽

Functional Theory ◽

Metal Organic

Solid-state mechanochemistry revealed a novel polymorph of the mercury(II) imidazolate framework, based on square-grid (sql) topology layers. Reaction monitoring and periodic density functional theory calculations show that the sql-structure is of higher stability than the previously reported three-dimensional structure, with the unexpected stabilization of a lower dimensionality structure explained by contributions of weak interactions, which include short C-H···Hg contacts.

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Stone–Wales defects preserve hyperuniformity in amorphous two-dimensional networks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2016862118 ◽

2021 ◽

Vol 118 (3) ◽

pp. e2016862118

Author(s):

Duyu Chen ◽

Yu Zheng ◽

Lei Liu ◽

Ge Zhang ◽

Mohan Chen ◽

...

Keyword(s):

2D Materials ◽

Single Layer ◽

Salient Feature ◽

Density Fluctuations ◽

Wave Number ◽

Static Structure Factor ◽

Two Dimensional ◽

Static Structure ◽

Topological Transformation ◽

Amorphous Graphene

Disordered hyperuniformity (DHU) is a recently discovered novel state of many-body systems that possesses vanishing normalized infinite-wavelength density fluctuations similar to a perfect crystal and an amorphous structure like a liquid or glass. Here, we discover a hyperuniformity-preserving topological transformation in two-dimensional (2D) network structures that involves continuous introduction of Stone–Wales (SW) defects. Specifically, the static structure factor S(k) of the resulting defected networks possesses the scaling S(k)∼kα for small wave number k, where 1≤α(p)≤2 monotonically decreases as the SW defect concentration p increases, reaches α≈1 at p≈0.12, and remains almost flat beyond this p. Our findings have important implications for amorphous 2D materials since the SW defects are well known to capture the salient feature of disorder in these materials. Verified by recently synthesized single-layer amorphous graphene, our network models reveal unique electronic transport mechanisms and mechanical behaviors associated with distinct classes of disorder in 2D materials.

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DFT Studies of Graphene-Functionalised Derivatives of Capecitabine

Zeitschrift für Naturforschung A ◽

10.1515/zna-2017-0290 ◽

2017 ◽

Vol 72 (12) ◽

pp. 1131-1138 ◽

Cited By ~ 1

Author(s):

Mehdi Aramideh ◽

Mahmoud Mirzaei ◽

Ghadamali Khodarahmi ◽

Oğuz Gülseren

Keyword(s):

Density Functional ◽

Density Functional Theory Calculations ◽

Atomic Scale ◽

Phase System ◽

Molecular Models ◽

Functional Theory ◽

Atomic Properties ◽

Scale Properties ◽

Derivatives Of

AbstractCancer is one of the major problems for so many people around the world; therefore, dedicating efforts to explore efficient therapeutic methodologies is very important for researchers of life sciences. In this case, nanostructures are expected to be carriers of medicinal compounds for targeted drug design and delivery purposes. Within this work, the graphene (Gr)-functionalised derivatives of capecitabine (CAP), as a representative anticancer, have been studied based on density functional theory calculations. Two different sizes of Gr molecular models have been used for the functionalisation of CAP counterparts, CAP-Gr3 and CAP-Gr5, to explore the effects of Gr-functionalisation on the original properties of CAP. All singular and functionalised molecular models have been optimised and the molecular and atomic scale properties have been evaluated for the optimised structures. Higher formation favourability has been obtained for CAP-Gr5 in comparison with CAP-Gr3 and better structural stability has been obtained in the water-solvated system than the isolated gas-phase system for all models. The CAP-Gr5 model could play a better role of electron transferring in comparison with the CAP-Gr3 model. As a concluding remark, the molecular properties of CAP changed from singular to functionalised models whereas the atomic properties remained almost unchanged, which is expected for a carrier not to use significant perturbations to the original properties of the carried counterpart.

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