Program
Please note that the program is tentative and subject to change anytime (even during the conference).
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IWLS 2022
June 30th-July 1st, 2022
The nature of the hydrogen interaction on the unreconstructed platinum (110) surface: ab-initio study
Tran Thi Thu Hanh
Ho Chi Minh City University of Technology (HCMUT)
Vietnam National University Ho Chi Minh City, Ho Chi Minh City, Vietnam
Abstract
The theoretical description of the interaction of the hydrogen atoms on the unreconstructed platinum surface Pt(110) was studied within the density functional theory (DFT) calculation. The most stable sites of the adsorbed hydrogen atom on the surface were confirmed: the H atom on the short bridge site (B), and the H atom on the top site (T). By performing the Monte Carlo (MC) simulation for the obtained gas model parameterized by the DFT method, the abundance of B over T was presented. The 5% underestimation of the hydrogen interaction energy in this work compared with the Cyclic Voltammetry experiment was shown. It can be caused by the omission of the hydration effect in the simulation calculation.
Keywords:
hydrogen adsorption, unreconstructed Pt(110) surface, density functional theory calculation, Monte-Carlo calculation, hydrogen interaction
Acknowledgement:
We acknowledge Ho Chi Minh City University of Technology (HCMUT), VNU-HCM for supporting this study
References:
[1] Lasia A 2004 J. Electroanal. Chem. 562 23.
[2] Hanh TTT and Hoa NV 2020 Adsorption—Journal of the International Adsorption Society 26 453.
IWLS 2022
June 30th-July 1st, 2022
Effect of magnetic field on twisted multilayer graphene
Distinguished Professor Godfrey Gumbs
Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065, USA
Abstract
This work aims at addressing an important advanced methodology for twisted multilayer graphene in the presence of applied magnetic field, which is the Bloch-basis tight-binding model (TBM) in conjunction with the generalized Peierls substitution. We investigate extensively the band structures, Landau levels (LLs), and quantum Hall conductivity (QHC) of twisted bilayer graphene and twisted double bilayer graphene, as well as their dependence on the twist angle. Comparison between these crucial properties of monolayer graphene, Bernal bilayer graphene, and the twisted systems is carefully made to highlight the roles played by twisting. Remarkably, for the first time, the effective TBM is combined with the generalized Peierls substitution to investigate the magnetic quantization of twisted graphene systems at magic angle. Our theoretical model opens up an opportunity for comprehension of the interplay between an applied magnetic field and the twisting effect associated with layered graphene. The proposed method is expected to be applicable for the calculation of magnetic quantization problems of other complex systems.
Keywords: Twisted graphene systems; magic angle; band structures; Landau levels; quantum Hall conductivity.
IWLS 2022
June 30th-July 1st, 2022
Long-term cycle-life experiment on a packed battery made by retired power batteries
Hsien-Ching Chung1,*
1 RD Manager, Super Double Power Technology Co., Ltd., Changhua City, Changhua County, 500042, Taiwan
*Author to whom correspondence should be addressed: hsienching.chung@gmail.com
As Lithium-ion (Li-ion) batteries become more popular in the world, the following problems on recycling are carried out [1, 2]. Echelon utilization is a suitable route to solve these problems since many retired power batteries still possess more than 80% of the initial energy capacity [3-5]. However, there still have many problems in how to recombine the retired power batteries. As many retired power batteries are packed, can this battery pack be treated as a single big battery? How does the big packed battery perform? What happen in the component batteries? To answer these problems, we setup a long-term cycle-life experiment on a packed battery and see what story it tell us.
Keywords: Lithium-ion battery, echelon utilization, retired power battery, cycle life
Acknowledgement:
The author (H. C. Chung) thanks Prof. Ming-Fa Lin for the workshop invitation and for inspiring him to study this topic. This work was supported in part by Super Double Power Technology Co., Ltd., Taiwan, under the project “Development of Cloud-native Energy Management Systems for Medium-scale Energy Storage Systems (https://osf.io/7fr9z/)” (Grant number: SDP-RD-PROJ-001-2020).
References:
[1] Chung H.C. (2020) Engineering integrations, potential applications, and outlooks of Li-ion batteries engrXiv DOI: 10.31224/osf.io/swcyg
[2] Chung H.C. and Cheng Y.C. (2020) Summary of Safety Standards for Repurposing Batteries Monthly J. Taipower's Eng. 860 35 DOI: 10.31224/osf.io/d4n3s
[3] Chung H.C. (2018) Failure mode and effects analysis of LFP battery module engrXiv DOI: 10.31224/osf.io/acxsp
[4] Chung H.C. (2021) Charge and discharge profiles of repurposed LiFePO4 batteries based on the UL 1974 standard Scientific Data 8 165 DOI: 10.1038/s41597-021-00954-3
[5] Chung H.C. and Cheng Y.C. (2019) Action Planning and Situation Analysis of Repurposing Battery Recovery and Application in China J. Taiwan Energy 6 425 DOI: 10.31224/osf.io/nxv7f
IWLS 2022
June 30th-July 1st, 2022
Proton-enabled biomimetic stabilization of small-molecule organic cathode in aqueous zinc-ion batteries
Nhu T. H. Luu 1,2, Alexander S. Ivanov 3, Teng-Hao Chen 4, Ilja Popovs 3, Jui-Chin Lee 5 and Watchareeya Kaveevivitchai 1,2*
1Department of Chemical Engineering, National Cheng Kung University, Tainan City 70101, Taiwan. 2Hierarchical Green-Energy Materials Research Centre, National Cheng Kung University, Tainan City 70101, Taiwan.
3Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, P.O. Box 2008, TN 37831, USA
4School of Pharmacy, National Cheng Kung University, Tainan City 70101, Taiwan.
5Core Facility Centre, National Cheng Kung University, Tainan City 70101, Taiwan.
Abstract
Small-molecule organic cathode materials offer flexible structural design features, high capacity, and sustainable production. Nonetheless, stability decrease due to high solubility of the electrode materials especially upon electrochemical cycling conditions limits their wide-range applications in energy storage technologies.1 We describe nature-inspired strategy to address cathode stability via introduction of transient vinylogous amide hydrogen bond networks in the small-molecule organic electrode material hexaazatrianthranylene (HATA) embedded quinone (HATAQ). Thanks to the proton-enabled biomimetic mechanism, HATAQ exhibits unparalleled cycling stability, ultra-high capacity and rate capability in the aqueous zinc-ion batteries, delivering 492 mAh g‒1 at 50 mA g‒1 and a reversible capacity of 199 mAh g‒1, corresponding to 99 % retention at 20 A g‒1 after 1000 cycles.2
HATAQ structure and electrochemical investigation.
Keywords: organic electrode material, aqueous zinc-ion battery
References
[1] Wu, M. S.; Luu, T. H. N.; Chen, T. H.; Lyu, H.; Huang, T. W.; Dai, S.; Sun, X. G.; Ivanov, A. S.; Lee, J. C.; Popovs, I.; Kaveevivitchai, W. Supramolecular Self‐Assembled Multi‐Electron‐Acceptor Organic Molecule as High‐Performance Cathode Material for Li‐Ion Batteries. Adv. Energy Mater. 2021, 2100330.
[2] Luu, T. H. N.; Ivanov, A. S.; Chen, T. H.; Popovs, I.; Lee, J. C.; Kaveevivitchai, W. Proton-enabled biomimetic stabilization of small-molecule organic cathode in aqueous zinc-ion batteries. J. Mater. Chem. A. 2022, 12371.
IWLS 2022
June 30th-July 1st, 2022
A hydrogen storage material: SiC monolayer
Nguyen Minh Phi1,2 , Tran Thi Thu Hanh1,2
1Laboratory of Computational Physics, Faculty of Applied Science, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam;
2Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam
Abstract
A monolayer structure of silicon carbide (SiC) had been studied as a hydrogen storage material using first principle calculations. The two dimension SiC model consists of 98 Si and C atoms, cut out from previous MD simulations [1], was tested for optimal geometry and k-point density by the SIESTA program [2]. The ground state total energy obtained from those results were then used in the adsorption energy calculations with consideration of zero-point energy using harmonic approximation. Several hydrogenated 2D-SiC configurations have been simulated, to understand the maximum number of adsorbed hydrogen atoms. The only binding sites for hydrogen adsorption have been found to be stable are the top sites (H is directly on top of Si and C atoms). The hydrogen adsorption energy is highest in TopSi position (about -0.709 eV). The calculations reveal that the chair conformer is the most stable adsorption configuration, reaching the hydrogen gravimetric capacity of 4.7 wt%. Those results show that 2D-SiC is a stable hydrogen absorbent with a low energy barrier. Further electrical properties studies are necessary to conclude about 2D-SiC hydrogen storage ability.
Keywords: Two-dimensional silicon carbide; Density Functional Theory; Zero-point energy
Acknowledgement:
We acknowledge Ho Chi Minh City University of Technology (HCMUT), VNU-HCM for supporting this study
References:
[1] Tranh, D. T. N., Hoang, V. V., and Hanh, T. T. T., “Modeling glassy SiC nanoribbon by rapidly cooling from the liquid: An affirmation of appropriate potentials”, Physica B Condensed Matter, vol. 608, 2021
[2] Soler, J. M., “The SIESTA method for ab initio order-N materials simulation”, Journal of Physics Condensed Matter, vol. 14, no. 11, pp. 2745–2779, 2002
IWLS 2022
June 30th-July 1st, 2022
Diverse electronic, optical, and thermoelectric properties of β-antimonene under external strains: A hybrid functional study
Duy Khanh Nguyen1,* and Nguyen Xuan Hao2
1High-Performance Computing Laboratory (HPC Lab), Information Technology Center, Thu Dau Mot University, Binh Duong Province, Vietnam
2Institute of Applied Technology, Thu Dau Mot University, Binh Duong Province, Vietnam
*khanhnd@tdmu.edu.vn; https://hpclab.tdmu.edu.vn
Abstract
The high-performance hybrid functional calculations are used to investigate the structural, electronic, optical, and thermoelectric properties of the β-antimonene monolayer under the external biaxial strain effects. The critical quantities to determine the studying properties are fully developed, including the cohesive energies, optimal lattice parameters, phonon band structures, electronic band structures, orbital-projected density of states, spatial valence charge distribution, charge density difference, real and imaginary parts of the dielectric functions, Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and figure of merit. Specifically, the β-antimonene monolayer is dynamically and structurally stable as examined via phonon spectrum and cohesive energy. At equilibrium, the β-Sb monolayer exhibits an indirect band gap of 1.310 and 1.786 eV as predicted by the PBE and HSE06 functionals, respectively. Applying external strains may induce the indirect-direct gap transition and significant variation of the bandgap. The calculated optical spectra indicate the enhancement of the optical absorption in a wide energy range from infrared to ultraviolet as induced by the applied strain. In the visible and ultraviolet regime, the absorption coefficient can reach values as large as 82.700 (104/cm) and 91.458 (104/cm). Besides, the thermoelectric performance may be improved considerably by applying proper external strain with the figure of merit reaching a value of 0.665. This study has fully revealed that the external biaxial strains are an effective approach to make the β-Sb monolayer prospective 2D material for high-performance optoelectronic and thermoelectric applications.
Keywords: 2D materials, β-antimonene, external strain, electronic properties, optical properties, and thermoelectric properties.
IWLS 2022
June 30th-July 1st, 2022
Interaction between peptides and an MoS2 monolayer containing a nanopore: First-Principles Calculations
Trinh Le Huyen 1, Chi-Hsuan Lee1, Shun-Jen Cheng 2, and Shun-Jen Cheng 1*
1 Graduate Institute of Applied Physics, National Chengchi University, Taipei 11605, Taiwan, ROC
2 Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan, ROC
* Email: ckyang@nccu.edu.tw
Abstract
Quantum chemical computations using first-principles calculations are employed to explore a few small peptide molecules and their interaction with two-dimensional (2D) monolayers of molybdenum disulfide (MoS2) with nanopores. A variety of monopeptides, dipeptides and a tripeptide are inserted into the hole of a MoS2 layer and the overall electronic structure calculated. The results show that bonding occurs between some molecules and the hole edge. We can also predict the outcome of reaction through the potential energy surface. These results strongly suggest that 2D MoS2 nanopores have a wide range of applications and deserve further study in experiments.
Keywords: 2-D MoS2 nanopore, peptide molecules, Nudged-Elastic Band, Potential energy surface
References
[1] K. Liu, L. Feng, A. Kis, A. Radenovic, “Atomically Thin Molybdenum Disulfide Nanopores with High Sensitivity for DNA Translocation,” ACS Nano. 8, 2504 (2014).
[2] J. Feng, K. Liu, R. D. Bulushev, S. Khlybov, D. Dumcenco, A. Kis, A. Radenovic, “Identification of single nucleotides in MoS2 nanopores. Nat. Nanotechnol. 10, 1070 (2015).
[3] A. B. Farimani, K. Min, N. R. Aluru, “DNA Base Detection Using a Single-Layer MoS2” ACS Nano. 8, 7914 (2014).
IWLS 2022
June 30th-July 1st, 2022
SYNTHESIS AND HYDROGELATION OF STAR-SHAPED POLY(L-LYSINE)-BASED AMPHIPHILIC COPOLYPEPTIDES
Thi Ha My Phan 1, Ching-Chia Huang 1, Yi-Jen Tsai 1, and Jeng-Shiung Jan 1,2*
1Department of Chemical Engineering, National Cheng Kung University, Tainan 70101, Taiwan
2Hierarchical Green-Energy Materials (Hi-GEM) Research Center, National Cheng Kung University, Tainan 70101, Taiwan
*Correspondence: jsjan@ncku.edu.tw
MOST 108-2221-E-006-034-MY3
Abstract
To study the effect of composition and topology of the polypeptide on the hydrogelation of amphiphilic copolypeptides, star-shaped diblock polypeptides based on hydrophilic, coil poly(L-lysine) (s-PLL) blocked with a hydrophobic, sheet-like polypeptide segment (poly(L-phenylalanine, poly(L-leucine), poly(L-valine) or poly(L-alanine)) were synthesized. Based on the results in this research, poly(L-phenylalanine), poly(L-leucine), and poly(L-valine) were found as good hydrogelators for promoting hydrogelation. Moreover, 6-armed polypeptides demonstrated their hydrogelation was better than 3-armed samples, and the 6-armed hydrogel containing poly(L-phenylalanine) showed the best hydrogelation ability. The arm numbers and hydrophilic polypeptide segments, which are dictated by the amphiphilic balance and interactions (hydrogen bonding, hydrophobic, cation-p, and p-p interactions) between polypeptide block, affected the hydrogelation and the mechanical properties of hydrogels. Due to creation of multiple interacting depots between hydrophobic polypeptide segments, the star-shaped topology also facilitated the hydrogelation of the block copolypetides. Consequently, this study highlights the polypeptide composition and topology could be additional parameters to manipulate polypeptide hydrogelation.
IWLS 2022
June 30th-July 1st, 2022
Tuning the electronic and optical properties of the GeS monolayer with biaxial strain
Duc-Quang Hoang1 Thanh-Dung Hoang2 and Khang D. Pham3,*
1 Applied Computational Civil and Structural Engineering Research Group, Faculty of Civil Engineering, Ton Duc Thang University, 19 Nguyen Huu Tho, District 7, Ho Chi Minh City 700 000, Vietnam
2 Department of Physics, Hanoi National University of Education, 136 Xuan Thuy Street, Cau Giay District, Hanoi 100 000, Vietnam
3 Department of Technology and Materials, Military Institute of Mechanical Engineering, Hanoi 100 000, Vietnam
Emails: hoangducquang@tdtu.edu.vn | dinhkhang307@gmail.com
Abstract:
We investigated the influence of biaxial strain on the electronic and optical properties of the GeS monolayer using first-principles calculations. Our results show that the GeS monolayer is a semiconducting material at equilibrium and semiconductor-metal phase transition may occur at large compression biaxial strain. The optical absorption of the GeS monolayer is high in the range of the middle ultraviolet lights. Besides, the biaxial strain has a great impact on the optical spectra of the GeS monolayer in the high energy domains. The semiconductor-metal phase transition and the computational results of the absorption of GeS can provide more useful information for applications in electromechanical and optoelectronic devices at the nanoscale.
Keywords: GeS monolayer , optical properties, band structure, strain effect
References:
1. K.D. Pham, et al. Superlattices and Microstructures 120 (2018): 501-507.
2. K.D. Pham, et al. Chemical Physics 524 (2019): 101-105.
IWLS 2022
June 30th-July 1st, 2022
A comparison study of the structural, electronic and electronic transport properties of nanoribbons based on Penta-graphene, Penta-P2C and Penta-SiC2
Tran Yen Mi, Huynh Anh Huy, Nguyen Thanh Tien
Can Tho University, Vietnam
Abstract
A comparison study of the structural, electronic and electronic transport properties of the three proposed sawtooth edge nanoribbon materials based on Penta-graphene, p-P2C and p-SiC2, i.e. PG-SS, p-P2C-SS and p-SiC2-SS is done. While these systems are the same in sawtooth-edges with dangling bond atoms neutralized by H ones, in atomic lines number and their precursor models pose P-421m symmetry, their geometry structures differ mainly at boundaries and their buckles are increased compared with the corresponding precursor
structures because of the quantum confinement effect. Both the electronic and electronic transport properties of these systems depend strongly on the sp2-hybridized atoms. In particular, we find out their special electronic characteristic is that conduction band minimum states are mainly contributed by sp2-hybridized atoms not located at edges. Moreover, in the case of electronic transport properties, we strongly believe that the more valence electrons are concentrated at atoms, the lower the transmission of these systems decreases, especially for sp2-hybridized atoms.
Keywords:
PG-SS, p-P2C-SS, p-SiC2-SS, sp2-hybridized atoms, structural properties, electronic properties, elertronic transport properties
References:
1. Rajbanshi, S. Sarkar, B. Mandal, P. Sarkar, Energetic and electronic structure of penta-graphene nanoribbons, Carbon 100 (2016) 118–125. doi: 10.1016/j.carbon.2016.01.014
2. T. Y. Mi, N. D. Khanh, R. Ahuja, N. T. Tien, Diverse structural and electronic properties of pentagonal sic2 nanoribbons: A first-principles study, Materials Today Communications 26 (2021) 102047. doi:10.1016/j.mtcomm.2021.102047
3. M. Naseri, S. Lin, J. Jalilian, J. Gu, Z. Chen, Penta-p2x (x= c, si) monolayers as wide-bandgap semiconductors: A first principles prediction, Frontiers of Physics 13 (3) (2018) 1–9. doi:10.1007/s11467-018-0758-2
4. N. T. Tien, P. T. B. Thao, V. T. Phuc, R. Ahuja, Electronic and transport features of sawtooth penta-graphene nanoribbons via substitutional doping, Physica E: Low-dimensional Systems and Nanostructures 114 (2019) 113572. doi:10.1016/j.physe.2019.113572
5. T. Y. Mi, D. M. Triet, N. T. Tien, Adsorption of gas molecules on pentagraphene nanoribbon and its implication for nanoscale gas sensor, Physics Open 2 (2020) 100014. doi:10.1016/j.physo.2020.100014
IWLS 2022
June 30th-July 1st, 2022
N-, B-, Al-, and Bi-adatom enriched
geometric and electronic properties of graphene nanoribbons.
Shih-Yang Lin
Department of Physics, National Cheng Kung University
Abstract:
Along with the remarkable fundamental properties from graphene, adatom-adsorbed graphene nanoribbons are expected to exhibit the tunable electronic and magnetic properties. The group III/V elements (B,N) and metal adatoms (Bi,Al) could provide multiple outermost orbitals for the multi-orbital hybridizations with the out-of-plane σ bondings on the carbon dangling bonds or honeycomb lattice. This dominate the fundamental properties of chemisorption systems, which are explored thoroughly in this study by using the first-principles calculations. The significant similarities and differences among B-, N-, Al-, Bi-adsorbed GNRs are discussed in details, including the optimal geometric structures, adsorption sites, nonuniform bond lengths, stability, band structures, conduction electron densities, spatial charge distributions, spin-and orbital-projected density of states, and magnetic configurations.
IWLS 2022
June 30th-July 1st, 2022
Exciton binding energy in two-dimensional semiconductors
Hieu T. Nguyen-Truong
Laboratory of Applied Physics, Science and Technology Advanced Institute,
Van Lang University, Ho Chi Minh City, Vietnam
Email: nguyentruongthanhhieu@vlu.edu.vn
Abstract
We approximately solve the Schrödinger equation for two-dimensional Wannier-Mott excitons in the effective mass approximation and derive an expression for the exciton energy levels, hence the exciton binding energy. The electron-hole interaction is described by the Rytova-Keldysh potential in a logarithmic approximation. From the derived expression, we introduce approximate expressions to experimentally determine the exciton binding energy (along with the quasiparticle band gap), the screening length, and the exciton reduced mass from measured exciton transition energies of the ground state (1s), and the first (2s) and the second (3s) excited states. Our results agree well with experimental data and theoretical calculations.
Keywords: 2D materials, exciton binding energy
References: Hieu T. Nguyen-Truong, Physical Review B 105, L201407 (2022)
IWLS 2022
June 30th-July 1st, 2022
Molecular-dynamical Investigations on the Thermo-physical Characteristics of Nanoscale Aluminum Powder during Laser Powder Bed Fusion Additive Manufacturing Process
Ling-Feng Lai1, Yu-Chen Su2, Chun-Ming Chang3, Kuei-Shu Hsu 4, Deng-Maw Lu5, Jian-Ming Lu6, *
1Doctoral Candidate/Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, No.1, Nantai St., Yungkang Dist., Tainan City 710301 Tainan;
2Assistant Professor/Department of Civil Engineering, Chung Yuan Christian University, No. 200, Zhongbei Rd., Zhongli Dist., Taoyuan City 320314, Tainan;
3Associate Research Fellow/Taiwan Instrument Research Institute, National Applied Research Laboratories, No. 20, R&D Rd. VI, Hsinchu Science Park, Hsinchu City 300092, Taiwan;
4Professor/Department of Recreation and Healthcare Management, Chia Nan University of Pharmacy & Science, No.60, Sec. 1, Erren Rd., Rende Dist., Tainan City 71710, Tainan;
5Professor/Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, No.1, Nantai St., Yungkang Dist., Tainan City 710301 Tainan;
6, *Research Fellow/National Center for High-Performance Computing, National Applied Research Laboratories, No. 28, Nan-ke 3rd Rd., Hsin-Shi Dist., Tainan City 744094, Taiwan.
(MOST Project No. : 110-2222-E-033-001-MY2)
Abstract
The molecular dynamics simulation method with EAM potential is to investigate the thermo-physical characteristics of aluminum nanopowders during laser bed fusion additive manufacturing process in this present study. Three aluminum nanopowders with different geometries, such as solid spheres, hollow spheres and solid ellipsoids, are selected shape selected and utilized to explore the morphological effect. Various diameters of solid spherical nanopowder made up to six cases, and similar combinations applied to hollow spherical nanopowder, as well. Moreover, four types of solid ellipsoidal nanopowder, such as parallel, skew, end-to-side, and side-to-side type are composed to twelve cases. Three different heating rates are used to observe the combination of aluminum nanopowders on the thermo-physical characteristics such as coalescence temperature and melting temperature of aluminum nanopowder at room temperature and in the process from the room temperature environment beyond the melting temperature during additive manufacturing process. Through the analysis of auxiliary conditions, such as neck width, potential energy, and radius of gyration, it is found that aluminum nanopowders, whether solid spheres, hollow spheres or solid ellipsoids, will solid-state sinter at room temperature. In constant nanoscale size additive manufacturing process, both the coalescence and melting temperature of aluminum nanopowder decreased with shrinking size or the reducing number of atoms. On the other hand, both the coalescence and melting temperature of aluminum nanopowder decreased with increasing the heating rate in the constant heating rate. In thermal equilibrium or high-temperature laser sintering process, the parallel type have the largest of neck width, yet but the end-to-end type have the smallest value of that. It is concluded that the size of nanopowder dominate the nanoscale meting temperature. The melting temperature of nanoscale aluminum is even significantly lower than the melting point of macroscopic aluminum. In this present study, both the particle size and heating rate of metallic nanopowder obviously affect the thermos-physical characteristics of metallic additive manufacturing process, the geometries and morphologies of metallic nanopowder play another effective role.
Keywords: molecular dynamics simulation method, additive manufacturing, nanoscale, coalescence temperature, melting temperature.
Acknowledgement: The financial and computational resource supports from NCHC, STUST, CYCU, and MOST (MOST project No. 110-2222-E-033-001-MY2). We would also thank the assistance from co-workers： Yu-Wen Chiang, Yu-Sheng Lin, Chi-Wen Yang, and Chao-Chen Li.
References:
[1]. Ling-Feng Lai, Molecular-dynamic Investigations on Three-dimensional Printing - A Case Study of Nanoscale Aluminum Powder Applied on Laser Powder Bed Fusion Additive Manufacturing Process, The thesis for the Degree of Master of Department of Applied Geoinformatics, Chia-Nan University of Pharmacy and Science, Tainan, Taiwan, January 2018.
[2]. Ling-Feng Lai, Deng-Maw Lu, Kuei-Shu Hsu, Jian-Ming Lu, A Study of Nanoscale Vanadium Powder Applied on 3D Printing Process, 2019 IEEE 2nd International Conference on Knowledge Innovation and Invention (ICKII), Seoul, Korea, 12-15 July 2019, pp.142-144.
[3]. Ling-Feng Lai, Deng-Maw Lu, Chun-Hsien Li, Kun-Hsien Chen, Shun-Chang Lin, Yu-Chen Su, Shan Jiang, Day-Shan Liu, Kuei-Shu Hsu, Jian-Ming Lu, Ming-Hsiao Lee, Zhen Chen, Physical characteristics of nanoscale titanium-aluminum alloy powder during 3D printing laser sintering process — A molecular dynamics study, 2018 IEEE International Conference on Applied System Invention (ICASI), Chiba, Japan, 13-17 April 2018, pp. 1318-1321.
[4]. Chao-Chen Li, Chun-Hsien Li, Shun-Chang Lin, Yu-Chen Su, Shan Jiang, Deng-Maw Lu, Jian-Ming Lu, Ming-Hsiao Lee, Zhen Chen, Physical characteristics of nanoscale niobium-zirconium alloy powder during 3D printing laser sintering process — A molecular dynamics study, 2018 IEEE International Conference on Applied System Invention (ICASI), Chiba, Japan, 13-17 April 2018, pp. 1322-1325.
[5]. Ling-Feng Lai, Deng-Maw Lu, Jian-Ming Lu, Molecular Investigations of Thermo-mechanical Characteristics of Nanoscale Iron Powders in Laser Powder Bed Fusion Additive Manufacturing Process: A Molecular Dynamic Simulation Study, 2022. (to be appeared)
[6]. Ling-Feng Lai, Deng-Maw Lu, and Jian-Ming Lu, Molecular Dynamic Simulation upon the Thermo-mechanical Characteristics of Hollow Palladium Nanopowders during Laser Powder Bed Fusion Additive Manufacturing Process, 2022. (to be appeared)
IWLS 2022
June 30th-July 1st, 2022
Outstanding Rate Capability of Silicon Anode by Interlayered Silver Nanoparticles for Lithium-Ion Thin-film Battery
Yi-xiu Chen
Department of Materials Science and Engineering, National Cheng Kung University (NCKU), Taiwan
IWLS 2022
June 30th-July 1st, 2022
Theoretical calculations of vibration and thermodynamics for absorbed hydrogen on Pt(100) surface
Van Hoa Nguyen 1,2 , Minh Phi Nguyen 1,2, Toan Vi Lam 1,2 and Thi Thu Hanh Tran 1,2.
1 Laboratory of Computational Physics, Faculty of Applied Science, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam.
2 Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam.
Abstract:
Pt(100) is one of the most popular facets of a real platinum electrode surface [1,2], which plays an essential role in a fuel cell. Thus, the adsorption of hydrogen on this surface is important to be researched in order to increase energy conversion efficiency. We have used the theoretical methods within the conventional ultrahigh vacuum (UHV) surface modeling to investigate the hydrogen adsorption of Pt(100). Both density functional theory (DFT) and Monte Carlo (MC) simulation are implemented to determine the stability, vibrational properties of adsorbed hydrogen atoms, and the H – H pair interactions. The DFT calculations were performed with GGA – PBE exchange – correlation energy functional [3] and under pseudopotential implemented in SIESTA software [4,5]. The converged data gained show that the adsorbed hydrogen atom tended to affect significantly on five Pt layers of the surface. Besides, it is found that the H adsorbed on the bridge (B) sites have the strongest binding energy, which is -0.67 eV. In addition, the streching frenquency and zero – point energy (ZPE) deduced by harmonic approximation indicate that the H on the top (T) sites vibrate with the highest vertically stretching frequency. In the increment of H coverage (ΘH), up to 1 ML (monolayer), only the H on B sites are accounted and the shape of the curve obtained in MC simulation shows a good agreement with the result of cyclic voltammetry measurement [6]. Reducing the pair interaction parameter by about 30%, the is also decreased and from 0.3 to 0.6 with respect to ΘH, the is well consistent with the experimental data [6]. This implies that the hydrogen atoms are mainly absorbed on the bridge sites of Pt(100) surface at medium range of H coverage.
Keywords: hydrogen adsorption, Pt(100), density functional theory, Monte Carlo simulation.
Acknowledgement:
We acknowledge Ho Chi Minh City University of Technology (HCMUT), VNU-HCM for supporting this study
References:
[1] J.M. Jaksic, N.M. Ristic, N.V. Krstajic, and M.M. Jaksic 1998 Int. J. Hydrog. Energy 23 1121.
[2] Henry C R 1998 Surf. Sci. Rep. 31 231.
[3] Perdew J P, Burke K and Ernzerhof M 1997 Phys. Rev. Lett. 78 1396.
[4] Ordejón P, Artacho E and Soler J M 1996 Phys. Rev. B 53 R10441(R).
[5] Soler J M, Artacho E, Gale J D, García A, Junquera J, Ordejón P and Sánchez-Portal D 2002 J. Phys. Condens. Matter 14 2745.
[6] Lasia A 2004 J. Electroanal. Chem. 562 23.
IWLS 2022
June 30th-July 1st, 2022
Solution-processed WO3@Si heterostructures as highly efficient room-temperature NO2 sensor
Chia-Yun Chen*
Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan
*E-mail: timcychen@mail.ncku.edu.tw
Abstract:
The urgent issue restricting the practical NO2 detection correlates with the requirement of elevated temperature above 1000C. Herein, we demonstrate the potential solution by carrying out the rational incorporation of silicon nanowires with WO3 nanoparticles via all-solution synthesis. The ultra-sensitive characteristics emerging the detection of wide-range NO2 concentration without exhibiting obvious saturation are displayed, where the abrupt variation of device resistivity and thus respond to the linear correlation between sensing response and involved NO2 concentration under trace NO2 environment (< 5ppm). By conducting both experimental validation and DFT calculation, the correlated detection mechanism is elucidated
It is found that the selective detection of NO2 gas is driven by the carrier collected at WO3 /Si interfaces and in turn cause the recombination, which leads to the reduction of depletion layer. All these involved processes can be taken place at room temperature and contributes to the substantial change of surface resistivity in gas sensor, which allows the robust reliability and repeatability for sensing wide concentration range of NO2 gas.
IWLS 2022
June 30th-July 1st, 2022
Structural modification enhances the optoelectronic properties
of defect blue phosphorene thin films
Minh Triet Dang
School of Education, Can Tho University, Viet Nam
Abstract
Active enhancement of the optical absorption coefficient to improve the light converting efficiency of thin-film solar cell materials is crucial to develop the next-generation solar cell devices. Here we report first-principles calculations with generalized gradient approximation to study the optoelectronic properties of pristine and divacancy blue phosphorene thin films under structural deformation. We show that instead of forming sp-like covalent bonds as in the pristine blue phosphorene layer, a divacancy introduces two particular dangling bonds between the voids. Using a microscopic (non-) affine deformation model, we reveal that the orbital hybridization of these dangling bonds is strongly modified in both the velocity and vorticity directions depending on the type of deformation, creating an effective light trap to enhance the material absorption efficiency. Furthermore, this successful light trap is complemented by a clear signature of plasmon when a divacancy blue phosphorene layer is slightly compressive. These results demonstrate a practical approach to tailor the optoelectronic properties of low-dimensional materials and to pave a novel strategy to design functionalized solar cell devices from the bottom-up with selective defects.
Keywords: blue phosphorene, first-principles, deformation model, optoelectronic properties
References:
[1] M.T. Dang, N.V. Duy, A. Zaccone, P. Schall, V.A. Dinh, Journal of Physics: Condensed Matter (2022), 34, 285702.
[2] M.T. Dang, R. Zargar, D. Bonn, A. Zaccone, P. Schall, Journal of Physics D: Applied Physics (2018), 51, 324002.
[3] D. Denisov, M.T. Dang, B. Struth, A. Zaccone, G. Wegdam, P. Schall, Scientific Reports (2015), 5, 14359.
IWLS 2022
June 30th-July 1st, 2022
Growth mechanism and physical properties of two dimensional semiconductors: What interesting results have been explored by my Vietnamese students?
Wu-Ching Chou
Department of Electrophysics, College of Sciences, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
Abstract
The growth mechanism and physical properties of two dimensional (2D) III-VI compound semiconductors were studied by molecular beam epitaxy (MBE), electron microscopy and optical spectroscopy. The in situ monitoring on the surface epitaxy by the reflective high energy electron diffraction (RHEED) reveals the dynamics of crystal phase and lattice symmetry. High crystal quality of 2D III-VI semiconductors, InSe1, GaSe2-4, or GaTe5 grown on GaN, GaAs, mica or glass was illustrated by the transmission electron micrographs (TEM). A wide range of band gap tenability from 1.3 to 2.0 eV, was demonstrated by the band edge emissions from the photoluminescence (PL) measurements.
References:
1. Sheng-Wei Hsiao et al., “Two-dimensional InSe thin films grown with indium precursor by molecular beam epitaxy”, Frontiers in Materials 9, 871003 (2022).
2. Nhu Quynh Diep et al., “Screw-Dislocation-Driven Growth Mode in two Dimensional GaSe on GaAs(001) Substrates Grown by Molecular Beam Epitaxy”, Scientific Reports 9, 17781 (2019).
3. Cheng-Wei Liu et al., “Substrate-induced strain in 2D layered GaSe materials grown by molecular beam epitaxy”, Scientific Reports 10, 12972 (2020).
4. Nhu Quynh Diep et al., “Pressure induced structural phase crossover of a GaSe epilayer grown under screw dislocation driven mode and its phase recovery”, Scientific Reports 11, 19887 (2021).
5. Sa Hoang Huynh et al., “Molecular Beam Epitaxy of Two-Dimensional GaTe Nanostructures on GaAs(001) Substrates: Implication for Near-Infrared Photodetection”, ACS Applied Nano Materials 4, 8913 (2021).
IWLS 2022
June 30th-July 1st, 2022
Phonon properties of group IV and group III-VI materials
Vo Khuong Dien
1Department of Physics, National Cheng Kung University
*vokhuongdien@gmail.com
Abstract:
Based on first-principles calculations, we study the vibrations properties and thermal heat capacity of two-dimensional honeycomb lattices: including group IV and group III-VI materials. We focus on the similarities and differences of their properties and try to understand the contribution of each phonon branch to the thermal properties. The theoretical frameworks are based on the optimal geometric structure, the phonon energy band structure, phonon density of states, phonon group velocity and the specific heat capacity.
Keywords: Group IV and group III-VI materials, hybridizations, vibrations, phonon properties
IWLS 2022
June 30th-July 1st, 2022
Rich quasi-particle in graphite-rare earth-metal compounds
Wang-Yu Ming1, Vo Khuong Dien1, Li Wei-Bang1, Jheng-Hong Ho1 and Ming-Fa Lin1, 2, *
1Department of Physics, National Cheng Kung University, 701 Tainan, Taiwan
2Hierarchical Green-Energy Materials Research Centre, National Cheng Kung University, Tainan City 70101, Taiwan.
*mflin@ncku.mail.edu.tw
Abstract
In any condensed-matter systems, the pure elements can create the 3D sp3-diamond and sp2 graphites, respectively, showing the wide-gap insulating behavior and the semi-metallic characteristics. The high anisotropy of very strong 3D covalent bodings and the interlayer 2pz-2pz orbital hybridizations are responsible for the featured band structures. The neighboring graphitic layers also exhibit three types of well-defined stacking configurations: AB, ABC, and AA. According to the theoretical predictions, the periodic arrangements determine the weak, but significant van der Waals interactions and thus the low-lying valence and conduction energy dispersions. The position-dependent C-C atomic interactions have been successfully established for layered graphenes, coaxial carbon nanotubes and carbon onions. Its drastic changes by the adatom intercalations frequently come to exist in the charging/discharging reactions of the anode/cathode material in the positive/negative-ion-based batteries. e. g., the graphite lithium/sodium/magnesium compounds. The up-to-date researches clearly indicate the planar carbon-honeycomb and intercalant lattices, where a stage-n compound is characterized by the n-layer graphitic sheets within two periodic intercalant layers. The van der Waals interactions are absent in stage-1 systems. The intralayer C-C and intercalant-intercalant bondings, the interlayer C-intercalant and C-C orbital hybridizations will dominate all quasiparticle properties. General speaking, the stage-n graphite compounds exhibit the free carrier dopings of conduction electrons or valence holes. Furthermore, their densities are very sensitive to the intercalant concentrations. The rare-earth metal guest atoms will be chosen for a model study of intercalation effects. Their active fourteen orbitals of 4f/5f, which frequently appear in the high-temperature superconductors, inter-metallic compounds and heavy Fermion compounds, are expected to the very complicated multi-orbital mixings and spin configurations. The concise pictures will be achieved from the featured crystal symmetries/band structures and wave functions/spatial charge and spin density distributions/atom- and orbital-decomposed magnetic moment/atom-, orbital- and spin-projected density of states/orbital-hybridization-related absorption peaks.
Keywords: VASP, graphite, orbital-hybridization, Rare earth, quasi-particle, electronic.
