Article
Materials Science, Multidisciplinary
Sara B. Isbill, Elodia Ciprian, Jonathan H. Christian, Amy Hixon, Bryan J. Foley, Eliel Villa-Aleman, Andrew J. Miskowiec
Summary: The structure of anhydrous Pu(C2O4)2 is still not completely understood, but recent studies using density functional theory (DFT) and experimental results have provided insight into its lattice dynamics. Differences in vibrational modes between candidate structures were identified, with one structure showing a distinctive mode at around 1380 cm-1. The agreement between the calculated frequency and optical activity of this mode and experimental results strongly supports this structure as that of anhydrous Pu(C2O4)2.
JOURNAL OF NUCLEAR MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Erik G. C. P. van Loon, Jan Berges, Tim O. Wehling
Summary: Constrained electronic-structure theories are used to construct effective low-energy models consisting of partially dressed particles, but interpreting the physical content of these theories can be complex. In this study, the properties of downfolding theories for electron-ion problems, particularly constrained density-functional perturbation theory (cDFPT), were carefully explored. The study found that dipole selection rules determine whether partially dressed phonons satisfy Goldstone's theorem, and electronic screening always lowers phonon frequencies. The theory was illustrated with cDFPT calculations for minimal example systems such as the nitrogen and benzene molecule, as well as graphene.
Article
Materials Science, Multidisciplinary
Aleksandar Zivkovic, Dejan Gemeri, Hilke Bahmann, Igor Lukacevic, Helen E. King
Summary: Vibrational spectroscopy is used to examine bone apatite mineralogy, but the spectra may be influenced by nanoscale crystallite size and surface phonon contributions. Density functional theory simulations were conducted to test for surface phonon effects on hydroxyapatite and carbonated apatite. Surface phonons were found to significantly contribute to the vibrational spectra, affecting the frequencies of internal modes of molecular groups. The presence of surface phonons is crucial for interpreting and applying the spectral effects in bone minerals.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Materials Science, Ceramics
Chun-Hai Wang, Wenhua Shu, Yuchang Qing, Fa Luo, Dongmei Zhu, Wancheng Zhou
Summary: In this study, the vibrational modes and lattice dynamics of C-type Y2O3 ceramics were investigated using vibrational spectra and DFT calculations. The frequency, phonon band structure, and density of phonon states were characterized, revealing the influence of different elements on the vibrational modes.
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
(2021)
Article
Materials Science, Multidisciplinary
Natalya Sheremetyeva, Drake Niedzielski, Damien Tristant, Liangbo Liang, Lauren E. Kerstetter, Suzanne E. Mohney, Vincent Meunier
Summary: The presence of silver intercalated in the van der Waals gap of few-layer MoS2 has a significant impact on the low-frequency Raman active modes of the material, leading to noticeable red-shifts with increasing silver concentration. Low-frequency vibrations can be used as a practical tool for determining silver concentration using Raman spectroscopy. Additionally, a semi-classical linear chain model can be used to extrapolate results to a large number of layers, providing valuable insights for further research in this area.
Article
Chemistry, Physical
Zilong Zhao, Kaiyu Wang, Guoyuan Wu, Dengbang Jiang, Yaozhong Lan
Summary: The adsorption behavior of Sc on the surface of kaolinite (001) was studied using density functional theory. Hydrated Sc3+, ScOH2+, and ScOH2+ species had coordination numbers of eight, six, and five, respectively. The adsorption model was based on ScOH2H2O5+, which had the most stable ionic configuration in the liquid phase. Adsorption of Sc ionic species was categorized into outer layer and inner layer adsorptions based on adsorption energy and bonding mechanism. Hydrated Sc ions were mainly adsorbed on the outer layer of the kaolinite (001)Al-OH and (00-1)Si-O surfaces through hydrogen bonding, while also being adsorbed on the inner layer of the deprotonated kaolinite (001)Al-OH surface through coordination bonding.
Article
Physics, Condensed Matter
Vivek Dwij, Binoy Krishna De, Gaurav Sharma, D. K. Shukla, M. K. Gupta, R. Mittal, Vasant Sathe
Summary: This study reexamined the phonon modes of BaTiO3 and reclassified the polar modes with experimental and theoretical calculations, providing authentic nomenclature for the phonon modes.
PHYSICA B-CONDENSED MATTER
(2022)
Article
Materials Science, Multidisciplinary
Mikhail M. Maslov, Alexey I. Kochaev, Margarita A. Gimaldinova, Anastasiya A. Grekova, Konstantin P. Katin
Summary: A series of new covalent crystals inspired by the carbon tesseract or hypercubane has been introduced and their packing structures and electronic characteristics have been analyzed. The hypercubane crystals were found to have simple cubic (sc), body-centered cubic (bcc), and face-centered cubic (fcc) packing. The sc and bcc crystals were identified as semiconductors with band gaps of 2.23 and 1.46 eV, respectively, while the fcc crystal exhibited metallic nature. The characteristic peaks in the Raman, IR, and UV-visible spectra were obtained for the identification of the different hypercubane crystals.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Leonid A. Chernozatonskii, Konstantin P. Katin, Victor A. Demin, Mikhail M. Maslov
Summary: By utilizing density functional theory, the study predicted the atomic and electronic structures, Raman, and IR spectra of the new diamond-like 2D materials known as Moire diamanes. The calculations revealed that these twisted diamanes have band gaps higher than standard diamanes, making them suitable for optical and optoelectronic devices, and exhibit blue-shifted Raman frequencies compared to traditionally stacked arrangements.
APPLIED SURFACE SCIENCE
(2021)
Article
Physics, Condensed Matter
Carla Yelpo, Ricardo Faccio, Daniel Ariosa, Sofia Favre
Summary: In this work, ab initio calculations were used to study the vibrational spectra of the Bi2212 compound, with a structural modulation correction to generate a more accurate representation of the real unit cell. A complete vibrational assignment was performed, along with an analysis of the electronic density of states and band structure comparing the tetragonal and distorted unit cell.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Chemistry, Multidisciplinary
Manish Kumar Tripathi, Venkatnarayan Ramanathan
Summary: The study reveals three minima for both dimers and trimers of methanethiol, with predictions at the B3LYP/cc-pVDZ level matching well with experimental values. The interaction energy between molecules decreases with an increase in basis set size, and the dipole moment of both dimer and trimer decreases at the B3LYP/cc-pVDZ level of theory. These new predictions are supported by AIM, FMO, MC, and NBO analysis.
Article
Chemistry, Multidisciplinary
Natalia Zawadzka, Lucja Kipczak, Tomasz Wozniak, Katarzyna Olkowska-Pucko, Magdalena Grzeszczyk, Adam Babinski, Maciej R. Molas
Summary: The optical response of bulk germanium sulfide (GeS) is systematically investigated using different polarization-resolved experimental techniques, showing that the low-temperature optical band-gap absorption is governed by a single resonance related to the neutral exciton, while the emission is dominated by the disorder/impurity- and/or phonon-assisted recombination processes. Furthermore, the Raman scattering spectra consist of six Raman peaks identified with the help of Density Functional Theory (DFT) calculations, allowing for the determination of GeS crystallographic directions.
Article
Chemistry, Multidisciplinary
Z. Liu, X. Zhang
Summary: A theoretical investigation of vanadium naphthalocyanine (VONc) was performed, including the molecular, electronic structures, and vibrational spectrum. The study compared VONc with other metal naphthalocyanines and found differences in symmetry and bond lengths. VONc exhibited the smallest HOMO-LUMO gap among the studied compounds. Accurate vibrational mode assignments were obtained using calculated potential energy distribution and animated pictures. A new symbol system was adopted to improve the clarity of the assignments, and corrections were made based on experimental comparisons.
MATERIALS TODAY CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Volodymyr Dzhagan, Nazar Mazur, Olga Kapush, Oleksandr Selyshchev, Anatolii Karnaukhov, Oleg A. Yeshchenko, Mykola I. Danylenko, Volodymyr Yukhymchuk, Dietrich R. T. Zahn
Summary: This study investigates the influence of the parameters of the shell and interface in semiconductor core/shell nanocrystals (NCs) on their optical properties and charge transfer, using Raman spectroscopy. The results show that the use of thioglycolic acid (TGA) during the synthesis leads to the formation of a CdS shell around the CdTe core in the NCs. The optical absorption and photoluminescence bands of these NCs are determined by the CdTe core, while the far-infrared absorption and resonant Raman scattering spectra are dominated by the vibrations related to the shell.
Article
Multidisciplinary Sciences
Jie Jiang, Lifu Zhang, Chen Ming, Hua Zhou, Pritom Bose, Yuwei Guo, Yang Hu, Baiwei Wang, Zhizhong Chen, Ru Jia, Saloni Pendse, Yu Xiang, Yaobiao Xia, Zonghuan Lu, Xixing Wen, Yao Cai, Chengliang Sun, Gwo-Ching Wang, Toh-Ming Lu, Daniel Gall, Yi-Yang Sun, Nikhil Koratkar, Edwin Fohtung, Yunfeng Shi, Jian Shi
Summary: This study experimentally investigated the pyroelectric behavior of three different pyroelectric materials at varying thicknesses. The results showed that the pyroelectric coefficient increased rapidly as the thickness of the free-standing sheets decreased. The study also found that materials with chemical bonds along the out-of-plane direction exhibited the greatest dimensionality effect on pyroelectricity.
Article
Materials Science, Multidisciplinary
Halyna Volkova, Kevin Pachuta, Kyle Crowley, Santosh Kumar Radha, Emily Pentzer, Xuan P. A. Gao, Walter R. L. Lambrecht, Alp Sehirlioglu, Marie-Helene Berger
Summary: Chemically exfoliated nanoscale few-layer thin LIxCoO2 samples were studied after annealing at various temperatures, revealing a gradual disordering of Li and Co cations in the lattice leading to a decrease in band gap and conductivity loss, with an increasing presence of Co(2+) in higher-temperature phases. The O-K spectra of the rocksalt phase indicate a potential loss of Li at higher temperatures. Conductivity measurements show a gradual drop above 200 degrees C, which is attributed to the presence of more Li-Co interdiffused phases with stronger correlation effects. Calculations based on DFT + U with Hubbard-U terms indicate a gap even in the paramagnetic phase of CoO.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Physics, Applied
Md Rezaul Karim, Brenton A. Noesges, Benthara Hewage Dinushi Jayatunga, Menglin Zhu, Jinwoo Hwang, Walter R. L. Lambrecht, Leonard J. Brillson, Kathleen Kash, Hongping Zhao
Summary: The research has determined the valence band offset between ZnGeN2 and GaN, providing new insights and methods for device designs based on the III-N/ZnGeN2 heterostructure.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Physics, Applied
Santosh Kumar Radha, Kyle Crowley, Brian A. Holler, Xuan P. A. Gao, Walter R. L. Lambrecht, Halyna Volkova, Marie-Helene Berger, Emily Pentzer, Kevin G. Pachuta, Alp Sehirlioglu
Summary: This article discusses the fundamental properties of 2D oxides and their preparation methods, as well as the effects on phonons, electronic band structures, and electronic screening. It also considers electronic structure theory and the importance of surface in ultrathin materials.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Amol Ratnaparkhe, Santosh Kumar Radha, Walter R. L. Lambrecht
Summary: This study presents a first-principles computational analysis of the vibrational properties of a-MoO3, focusing on the zone center modes that can be measured by a combination of infrared and Raman spectroscopy, with simulated polarization dependent spectra. Calculations were also performed for a monolayer form of Mo2O6 with shifts in phonon frequencies analyzed.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Klichchupong Dabsamut, Adisak Boonchun, Walter R. L. Lambrecht
Summary: In this study, the doping of ultrawide bandgap semiconductor LiGaO2 with N-2, NO, and O-2 molecules placed in either Ga or Li vacancies was investigated using first-principles calculations. The results show that these molecular dopants have deep acceptor level transition states and are closely related to the properties of corresponding vacancies.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Vitaly Gorelov, Lucia Reining, Martin Feneberg, Ruediger Goldhahn, Andre Schleife, Walter R. L. Lambrecht, Matteo Gatti
Summary: This article uses V2O5 as an example to explore how charge-transfer excitations combine to form excitons with large binding energy and electron-hole distance, and explains this phenomenon. By combining various methods, consistent results are obtained.
NPJ COMPUTATIONAL MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Phillip Popp, Walter R. L. Lambrecht
Summary: This study presents a first-principles computational investigation of different phases of LiAlO2, including their energy, lattice volume, and electronic band structures. The lowest energy phase is found to be the gamma phase, while the octahedral alpha phase is a high-pressure phase. Si doping is found to significantly alter the conduction band and reduce the band gap.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Klichchupong Dabsamut, Adisak Boonchun, Walter R. L. Lambrecht
Summary: Various defects in ZnO, including substitutional N on the O site (N-o) and N-2 at different positions (O site, interstitial sites, and Zn site), are studied using first-principles calculations. The study aims to understand the electron paramagnetic resonance (EPR) center reported for N-2 in ZnO. The calculated g tensors are compared with experiments and provide insights into the behavior of N-2 in ZnO. The study resolves previous controversies regarding the site location and nature of the EPR center.
PHYSICAL REVIEW MATERIALS
(2022)
Editorial Material
Chemistry, Physical
Walter R. L. Lambrecht
Summary: Lu et al. (2022), 24, 5529 use incorrect explanations for their findings by incorrectly applying ideas from tight-binding methods. An alternative qualitative explanation based on strain variations and a tight-binding model with nearest neighbor interactions is provided.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Vitaly Gorelov, Lucia Reining, Walter R. L. Lambrecht, Matteo Gatti
Summary: In this study, we investigate the effect of screening on absorption and electron energy loss spectroscopy, focusing on the impact of local distortions on screening and the resulting changes in various spectra. Using V2O5 as a prototype material, we demonstrate how local distortions affect screening and how changes in screening affect electron energy loss and absorption spectra, including excitons. We highlight the robustness of many-body effects in the spectra with respect to structural modifications, while significant changes in the band structure and the nature of excitations may occur. This provides insight into the structure-properties relations crucial for the use of V2O5 as an energy storage material and for optimizing the analysis and calculation of electronic spectra in complex materials.
Article
Materials Science, Multidisciplinary
Ozan Dernek, Walter R. L. Lambrecht
Summary: This study evaluates the potential of MgSiN2-GaN alloys for deep ultraviolet optoelectronic applications, and finds that they have large band gaps and small mixing energies, which could avoid the tensile strain that limits the application of AlxGa(1-x)N on GaN.
Article
Materials Science, Multidisciplinary
Ozan Dernek, Dmitry Skachkov, Walter R. L. Lambrecht, Mark van Schilfgaarde
Summary: The quasiparticle self-consistent GW approach improves the results of density functional theory by correcting the quasiparticle energies. By representing the self-energy corrections in real space, it is possible to construct the self-energy of a complex system using a cut-and-paste method. In GaAs, the defect part can be well represented by a minimal eight-atom cell and used to construct the self-energy for a 64-atom cell.
Article
Materials Science, Multidisciplinary
Santosh Kumar Radha, Walter R. L. Lambrecht, Brian Cunningham, Myrta Gruning, Dimitar Pashov, Mark van Schilfgaarde
Summary: The optical response functions and band structures of LiCoO2 were studied using various levels of approximation, from DFT in GGA to QSGW with and without ladder diagrams as well as the BSE approach. The QSGW method overestimated the band gap, with electron-hole or excitonic effects influencing the quasiparticle gap and absorption peaks. The excitons were found to be strongly localized and comparisons to experimental data were made.
Article
Materials Science, Multidisciplinary
Santosh Kumar Radha, Walter R. L. Lambrecht
Summary: Annihilating a pair of Dirac fermions leads to a topological transition from the critical semimetallic phase to an obstructed atomic limit insulator phase, instead of a trivial insulator phase. This transition is attributed to branch cuts in the phase of wave functions, resulting in nontrivial Zak phase along certain directions.
Article
Materials Science, Multidisciplinary
Santosh Kumar Radha, Amol Ratnaparkhe, Walter R. L. Lambrecht
Summary: Quasiparticle self-consistent GW calculations were used to analyze the band structures of LiGaO2 and NaGaO2. The results show these materials are promising candidates for ultrawide-gap semiconductors with wurtzite-based tetrahedrally bonded crystal structures, and alternative crystal structures were also investigated. The study provides insights into the optical response functions and transition pressures to different phases for these compounds.
