Article
Materials Science, Multidisciplinary
Xuelu Wang, Chunjin Chen, Binbin Jiang, Huichao Duan, Kui Du
Summary: Phase engineering of nanomaterials is gaining increasing research interest due to the influence of crystal structures on the physical and chemical properties of metals. In this study, a novel simple hexagonal structured gold was fabricated through in situ selective etching on an ordered Cu-Au intermetallic compound, demonstrating a low coordination number and packing fraction. The discovery of this new crystal structure suggests that metals can form diverse structures by changing their effective atomic volume, providing opportunities for engineering new physical properties and applications.
Article
Materials Science, Multidisciplinary
Hajer Saadi, Othmen Khaldi, Tarek Larbi, Zohra Benzarti
Summary: This study investigates the impact of incorporating cobalt on various characteristics of ZnO nanoparticles. The results show that cobalt doping affects the crystallite size, optical properties, and dielectric properties, providing a comprehensive experimental and theoretical description of Co-doped ZnO nanoparticles.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2023)
Article
Chemistry, Physical
Tianxiao Liang, Zihan Zhang, Hongyu Yu, Tian Cui, Xiaolei Feng, Chris J. Pickard, Defang Duan, Simon A. T. Redfern
Summary: The research reveals that at high pressure, sodium, silicon, and hydrogen can form superionic compounds, with Na2SiH6 being dynamically stable at low pressure and becoming superionic at 5 GPa, re-entering solid/fluid states at about 25 GPa. This observation of H- transport opens up the possibility of new H- conductors and has implications for the formation of conducting layers in carbon exoplanets, potentially enhancing their habitability.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Tingting Yuan, Jingwen Wu, Xujun Xu, Jianjun Liu, Yong Du
Summary: Based on the controllable conductivity of photosensitive semiconductors and the phase transition characteristic of vanadium oxide, a metamaterial absorber with switchable single-band and dual-band absorption in the terahertz region is designed. By adjusting the external pump light power and the conductivity of gallium arsenide and vanadium oxide, the absorptivity can be increased to above 99%. The designed absorber can be switched from triple-band to single-band absorption by changing the conductivity state of gallium arsenide and vanadium oxide. The absorber also exhibits excellent absorption characteristics for both TE and TM fields in a wide-angle incidence range.
RESULTS IN PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Yu Wang, Zhigang Song, Jiawei Wan, Sophia Betzler, Yujun Xie, Colin Ophus, Karen C. Bustillo, Peter Ercius, Lin-Wang Wang, Haimei Zheng
Summary: This study presents a new method for synthesizing moire superlattices with strong chemical bonding, using lead sulfide as an example. Water-soluble ligands are used as a removable template to obtain ultrathin PbS nanosheets, which are then assembled into direct-contact bilayers with various twist angles. Atomic-resolution imaging reveals periodic structural reconstruction at the superlattice interface due to the strong metavalent coupling. The twist-angle-dependent electronic structure, particularly the emergence of separated flat bands, is demonstrated through electron energy loss spectroscopy and theoretical calculations. The localized states of flat bands resemble well-arranged quantum dots, suggesting potential applications in devices.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2022)
Article
Chemistry, Physical
Bo Peng, Shuichi Murakami, Bartomeu Monserrat, Tiantian Zhang
Summary: Degenerate points/lines in the band structures of crystals have become a staple feature of topological materials, with a relation between bulk topology and surface states. While line degeneracies of bulk excitations have been extensively studied, line degeneracies of surface states are still not well understood. This study shows that surface degeneracies can be protected by symmetries such as time-reversal symmetry and glide mirror symmetry, providing an ideal platform to explore such degeneracies.
NPJ COMPUTATIONAL MATERIALS
(2021)
Article
Physics, Multidisciplinary
M. Denk, E. Speiser, J. Plaickner, S. Chandola, S. Sanna, P. Zeppenfeld, N. Esser
Summary: This study reports the first evidence of Raman scattering from surface phonons of a pristine metal surface, and reveals a Raman-active surface vibrational resonance on Cu(110) with a surprisingly large scattering efficiency.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Physical
Emine Tanis
Summary: This study investigates the effects of various solvents on the properties of the PHMB organic material, including electronic, optical, electrical, and sensing properties. The experimental measurements and quantum chemical calculations provide valuable insights for understanding and applying new-generation optoelectronic devices.
JOURNAL OF MOLECULAR LIQUIDS
(2022)
Article
Engineering, Electrical & Electronic
S. Prathap, W. Madhuri
Summary: Pb1-xCoxFe12O19 nano-crystallites with an average crystal diameter varying between 74 and 86 nm were prepared via sol-gel auto-combustion, showing a single-phase structure confirmed by XRD analysis. The surface morphology of the ferrites revealed a long hexagonal structure and dielectric characterization indicated that the composition x=0.75 is suitable for high definition television deflection yokes due to its high dielectric constant and low electrical conductivity.
JOURNAL OF ELECTRONIC MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
I. Kammoun, M. Belhouchet, A. Ben Ahmed, J. Lhoste, M. Gargouri
Summary: A new organic-inorganic hybrid compound, [C12H17N2](2)ZnBr4, was synthesized and studied using single-crystal X-ray diffraction, optical absorption, and complex impedance spectroscopy. The compound has a centrosymmetric crystal structure in the P2(1)/n space group at room temperature, consisting of [ZnBr4](2-) anions and (C12H17N2)(+) cations. The crystal packing is stabilized by hydrogen bonding and the compound exhibits semiconductor properties with a band gap of 3.94 eV.
Article
Optics
I Ghazal, H. Absike, A. Rachadi, H. Ez-Zahraouy
Summary: This study investigated the structural, electronic, optical, and thermoelectric properties of the ACuS(2)(A=Al, Ga, In) ternary chalcopyrite compounds using DFT and Boltzmann transport theory. The results indicate promising applications of these compounds in photovoltaic, optoelectronic, and thermoelectric devices.
Article
Chemistry, Multidisciplinary
Fabian Borrmann, Takuya Tsuda, Olga Guskova, Nataliya Kiriy, Cedric Hoffmann, David Neusser, Sabine Ludwigs, Uwe Lappan, Frank Simon, Martin Geisler, Bipasha Debnath, Yulia Krupskaya, Mahmoud Al-Hussein, Anton Kiriy
Summary: The understanding and applications of electron-conducting pi-conjugated polymers with naphtalene diimide (NDI) blocks have made remarkable progress. A study has been conducted to develop an n-type conducting NDI polymer with enhanced stability of its n-doped states for prospective in-water applications. The study uses a combined experimental-theoretical approach to identify critical features and parameters that control the doping and electron transport process.
Article
Optics
Dan Wang, Weiqing Lu, Jingya Han, Yao Zhang, Yi Liu, Haitao Zhou, Jinze Wu, Junxiang Zhang
Summary: In this study, we actively controlled atomic coherence and interference in degenerate four-wave mixing (DFWM) through energy-level modulation, resulting in enhanced DFWM gain for the generation of near-resonant squeezed twin beams.
Article
Chemistry, Physical
Kuo-Chuan Chang, Chia-Jyi Liu
Summary: BiCuSeO demonstrates remarkable low thermal conductivity among oxides, with Cu atoms playing a more significant role in reducing lattice thermal conductivity than the lone pair of Bi3+ and point defects brought about by elemental doping.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Multidisciplinary
Chih Shan Tan, Chung Chi Yang
Summary: Dynamical stability is crucial in phase transition and structure. This research predicts promising cation candidates in lead-free perovskite materials through lead ion replacement. Alkaline-earth cations, stable positive divalent ions, can enhance dynamical stability by reducing the imaginary part of phonon density of states.
Article
Materials Science, Ceramics
Yasser S. Alajerami, David A. Drabold, Rajendra Thapa, M. I. Sayyed, M. H. A. Mhareb
Summary: The study introduced a new gamma-ray shielding glass composed of a borate-base modified with sodium oxide, cadmium oxide, and various concentrations of bismuth oxide. The results showed an enhancement in shielding parameters with an increase in bismuth oxide content, suggesting the use of glasses with higher bismuth oxide for gamma radiation shielding facilities.
INTERNATIONAL JOURNAL OF APPLIED GLASS SCIENCE
(2021)
Article
Multidisciplinary Sciences
Volker L. Deringer, Noam Bernstein, Gabor Csanyi, Chiheb Ben Mahmoud, Michele Ceriotti, Mark Wilson, David A. Drabold, Stephen R. Elliott
Summary: This study investigates the structural transitions of amorphous silicon under increasing external pressure, revealing a three-step transformation sequence and demonstrating the transient nature of the VHDA phase, which rapidly nucleates crystallites. The machine learning model for electronic density of states provides support for the onset of metallicity during VHDA formation and subsequent crystallization, showcasing a machine learning-driven approach to predictive materials modeling.
Article
Physics, Condensed Matter
Yasser Saleh Mustafa Alajerami, David A. Drabold, M. H. A. Mhareb, Katherine Leslee A. Cimatu, Gang Chen, K. M. Abushab
Summary: New bismuth borate glass systems containing various concentrations of cadmium oxide were prepared using the melt-quenching method, showing good transparency and radiation shielding properties. Experimental results were in good agreement with simulation, with the mean free path of S4 system showing promising results compared to barite and chalcocite concretes.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2021)
Article
Physics, Condensed Matter
Kashi N. Subedi, Kiran Prasai, David A. Drabold
Summary: The study utilized the Kubo-Greenwood formula to project electronic conductivity and discussed a Hermitian positive semidefinite matrix G to simplify the computation of spatial conduction activity. It found that certain structures, such as sp(2) rings and sp chains, are conduction-active sites in low-density amorphous carbon, and transport in amorphous silicon involves hopping through tail states mediated by defects near the Fermi level. The method is shown to be easily implementable with various electronic structure codes, providing estimates for single-particle electronic states and energies.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2021)
Article
Physics, Condensed Matter
Rajendra Thapa, Kashi Nath Subedi, Bishal Bhattarai, David A. Drabold
Summary: The structure of Cu46Zr46Al8 was inverted using X-ray structure factor data and energy minimizations with FEAR, generating models in good agreement with diffraction experiment data. Voronoi tessellation analysis showed reasonable agreement with previous results, and the models included structural units believed to be crucial for the excellent glass forming ability of this metallic glass. Constant temperature MD revealed a significant increase in the fraction of specific clusters near the glass transition, while SPC calculations indicated that Zr dominates conduction.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2021)
Article
Physics, Multidisciplinary
R. Thapa, C. Ugwumadu, K. Nepal, J. Trembly, D. A. Drabold
Summary: An amorphous graphite material with layering transition and unique structural disorder has been predicted, which may have implications for other layered materials.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Applied
Kashi N. Subedi, Kishor Nepal, Chinonso Ugwumadu, Keerti Kappagantula, D. A. Drabold
Summary: We used density-functional theory (DFT) to investigate the electronic transport properties of copper-graphene (Cu-G) composites. By varying the interfacial distance of copper/graphene/copper (Cu/G/Cu) interface models, we studied the conduction in composites. Our calculations using the Kubo-Greenwood formula showed that the conductivity of the models increased as the Cu-G distance decreased and saturated below a certain threshold. Bader charge analysis based on DFT revealed increasing charge transfer between Cu atoms and graphene as the Cu-G distance decreased. The electronic density of states showed increased contributions from both copper and carbon atoms near the Fermi level with decreasing Cu-G interfacial distance. Space-projected conductivity calculations demonstrated that graphene acted as a bridge for electronic conduction at small Cu-G distances, thus enhancing conductivity.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Ceramics
R. Thapa, C. Ugwumadu, K. Nepal, D. A. Drabold, M. T. M. Shatnawi
Summary: The structural, vibrational, and electronic properties of glassy GeSe4 and GeSe3 were investigated using a method that combines the Reverse Monte Carlo algorithm, density functional theory, and experimental data. The models generated using the force enhanced atomic refinement technique showed excellent agreement with X-ray and neutron diffraction data and accurately captured important structural features of the system. These findings suggest that the new approach is superior to the melt-quench model in describing the properties of glassy GeSe4 and GeSe3.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2023)
Article
Physics, Condensed Matter
Chinonso Ugwumadu, Rajendra Thapa, Yahya Al-Majali, Jason Trembly, D. A. Drabold
Summary: The important variables of amorphous carbon nanotubes (a-CNT) with up to four walls and sizes ranging from 200 to 3200 atoms were successfully predicted using machine learning random forest technique. The topological defects and electronic properties of these a-CNTs were analyzed. The vibrational density of states and thermal conductivity at 300 K were calculated.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Chemistry, Physical
C. Ugwumadu, R. Thapa, K. Nepal, A. Gautam, Y. Al-Majali, J. Trembly, D. A. Drabold
Summary: This study presents a novel method for constructing atomistic models of nanoporous carbon and investigates their properties and behavior. The models were created by randomly distributing carbon atoms and pore volumes in a periodic box and then using simulation tools to find the energy-minimum structures. The analysis revealed the structural characteristics, pore size distribution, and surface properties of the models, as well as their electronic, vibrational, thermal, and mechanical properties.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Materials Science, Multidisciplinary
C. Ugwumadu, K. Nepal, R. Thapa, Y. G. Lee, Y. Al Majali, J. Trembly, D. A. Drabold
Summary: This study simulated the formation process of multi-shell Fullerene buckyonions using a density-functional-theory (DFT)-trained machine-learning carbon potential within the Gaussian Approximation Potential (GAP) Framework. Fullerene clusters of seven different sizes were formed through self-organization and layering from the outermost shell to the innermost. The inter-shell cohesion is partially due to interaction between delocalized π electrons protruding into the gallery.
Article
Materials Science, Multidisciplinary
Logan E. Veley, Chinonso Ugwumadu, Jason P. Trembly, David A. Drabold, Yahya Al-Majali
Summary: This article discusses the use of coal-plastic composite materials in 3D printing. By incorporating coal as a filler into different types of polymer resins, the researchers successfully fabricated composite filaments. The study found that the addition of coal improved printing issues with high-density polyethylene and that the mechanical properties of the composite materials were influenced by the amount of coal added.
ACS APPLIED POLYMER MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Kashi N. Subedi, Keerti Kappagantula, Frank Kraft, Aditya Nittala, David A. Drabold
Summary: This study investigates the effects of disorder on the conductivity of crystalline metals and provides insights into its underlying mechanisms. By employing density functional theory and thermal molecular dynamics simulations, the authors reveal the local and spatial impacts of disorder on conduction, as well as the spatial nature of thermal fluctuations.
Article
Materials Science, Multidisciplinary
Rajendra Thapa, Kiran Prasai, Riccardo Bassiri, Martin M. Fejer, D. A. Drabold
Summary: The atomic structure of ZrO2:Ta2O5 thin films was studied using computer models and x-ray scattering data. Structural differences were observed between the as-deposited and annealed samples, particularly in their metal-metal correlations. The band gap and density of states of ZrO2:Ta2O5 were similar to pure Ta2O5 and remained unchanged after annealing.
Article
Materials Science, Multidisciplinary
K. N. Subedi, V Botu, D. A. Drabold
Summary: Atomistic simulations of (Na2O)(x)(SiO2)(1-x) glasses using the building-block method reveal agreement between the local structure, defects near the band gap, and thermal properties with experimental data. Elastic properties of the glasses are studied by calculating bulk and shear modulus.
