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Luo, Wei
Publications (10 of 47) Show all publications
Bovornratanaraks, T., Tsuppayakorn-aek, P., Luo, W. & Ahuja, R. (2019). Ground-state structure of semiconducting and superconducting phases in xenon carbides at high pressure. Scientific Reports, 9, Article ID 2459.
Open this publication in new window or tab >>Ground-state structure of semiconducting and superconducting phases in xenon carbides at high pressure
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 2459Article in journal (Refereed) Published
Abstract [en]

The 'missing Xe paradox' is one of the phenomena at the Earth's atmosphere. Studying the 'missing Xe paradox' will provide insights into a chemical reaction of Xe with C. We search the ground-state structure candidates of xenon carbides using the Universal Structure Predictor: Evolutionary Xtallography (USPEX) code, which has been successfully applied to a variety of systems. We predict that XeC2 is the most stable among the convex hull. We find that the I((4) over bar)2m structure of XeC2 is the semiconducting phase. Accurate electronic structures of tetragonal XeC2 have been calculated using a hybrid density functionals HSE06, which gives larger more accurate band gap than a GGA-PBE exchange-correlation functional. Specifically, we find that the I((4) over bar)2m structure of XeC2 is a dynamically stable structure at high pressure. We also predict that the P6/mmm structure of XeC2 is the superconducting phase with a critical temperature of 38 K at 200 GPa. The ground-state structure of xenon carbides is of critical importance for understanding in the missing Xe. We discuss the inference of the stable structures of XeC2. The accumulation of electrons between Xe and C led to the stability by investigating electron localization function (ELF).

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-378979 (URN)10.1038/s41598-019-39176-4 (DOI)000459281500028 ()30792456 (PubMedID)
Funder
Swedish Research Council
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11Bibliographically approved
Long, D., Li, M., Meng, D., He, Y., Yoon, I. T., Ahuja, R. & Luo, W. (2018). Accounting for the thermo-stability of PdHx (x=1-3) by density functional theory. International journal of hydrogen energy, 43(39), 18372-18381
Open this publication in new window or tab >>Accounting for the thermo-stability of PdHx (x=1-3) by density functional theory
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2018 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 43, no 39, p. 18372-18381Article in journal (Refereed) Published
Abstract [en]

We calculate the formation enthalpies of PdHx (x = 0-3) by cluster expansion (CE) and calculations based on density functional theory. CE predicts the stable palladium hydride structures PdH, PdH2.62, and PdH2.75. The band structures and density of states indicate that the amount of hydrogen in the palladium lattice does not alter the metallic character of the palladium significantly. However, all PdH X structures with x > 1 have greater formation enthalpies than that of the given reaction path 4PdH(2) = 2PdH + 2Pd + 3H(2) and thus they are thermodynamically unstable. The shorter bond length of Pd-H and the smaller bond angle of Pd-H-Pd imply a higher cohesive energy in zincblende (ZB) PdH than that in rocksalt (RS) PdH. Bader charge analysis shows a stronger electronegativity of H atoms in ZB-PdH than that in RS-PdH. This results in a stronger Pd-H bond in ZB-PdH than that in RS-PdH. Thus ZB-PdH has lower formation enthalpy than that of RS-PdH. However, regarding the dynamic stability, we conclude that hydrogen atoms prefer to occupy the octahedral sites of the palladium lattice because of the lower zero-point energy and vibration free energy than that of occupying the tetrahedral sites. 

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
PdHx, Cluster expansion method, Density functional theory, Formation enthalpy, Thermodynamic stability, Dynamic stability
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-368759 (URN)10.1016/j.ijhydene.2018.08.030 (DOI)000446949400032 ()
Available from: 2018-12-07 Created: 2018-12-07 Last updated: 2018-12-07Bibliographically approved
Yang, X., Li, H., Hu, M., Liu, Z., Wärnå, J., Cao, Y., . . . Luo, W. (2018). Mechanical properties investigation on single-wall ZrO2 nanotubes: A finite element method with equivalent Poisson's ratio for chemical bonds. Physica. E, Low-Dimensional systems and nanostructures, 98, 23-28
Open this publication in new window or tab >>Mechanical properties investigation on single-wall ZrO2 nanotubes: A finite element method with equivalent Poisson's ratio for chemical bonds
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2018 (English)In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 98, p. 23-28Article in journal (Refereed) Published
Abstract [en]

A method to obtain the equivalent Poisson's ratio in chemical bonds as classical beams with finite element method was proposed from experimental data. The UFF (Universal Force Field) method was employed to calculate the elastic force constants of Zr-O bonds. By applying the equivalent Poisson's ratio, the mechanical properties of single-wall ZrNTs (ZrO2 nanotubes) were investigated by finite element analysis. The nanotubes' Young's modulus (Y), Poisson's ratio (nu) of ZrNTs as function of diameters, length and chirality have been discussed, respectively. We found that the Young's modulus of single-wall ZrNTs is calculated to be between 350 and 420 GPa.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Signal-wall ZrO2 nanotubes, Mechanical properties, Finite element method, Poisson's ratio
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-347532 (URN)10.1016/j.physe.2017.10.005 (DOI)000425118100005 ()
Funder
Swedish Research Council
Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2018-04-04Bibliographically approved
Naqvi, S. R., Hussain, T., Luo, W. & Ahuja, R. (2018). Metallized siligraphene nanosheets (SiC7) as high capacity hydrogen storage materials. Nano Reseach, 11(7), 3802-3813
Open this publication in new window or tab >>Metallized siligraphene nanosheets (SiC7) as high capacity hydrogen storage materials
2018 (English)In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 11, no 7, p. 3802-3813Article in journal (Refereed) Published
Abstract [en]

A planar honeycomb monolayer of siligraphene (SiC7) could be a prospective medium for clean energy storage due to its light weight, and its remarkable mechanical and unique electronic properties. By employing van der Waals-induced first principles calculations based on density functional theory (DFT), we have explored the structural, electronic, and hydrogen (H-2) storage characteristics of SiC7 sheets decorated with various light metals. The binding energies of lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca),scandium (Sc), and titanium (Ti) dopants on a SiC7 monolayer were studied at various doping concentrations, and found to be strong enough to counteract the metal clustering effect. We further verified the stabilities of the metallized SiC7 sheets at room temperature using ab initio molecular dynamics (MD) simulations. Bader charge analysis revealed that upon adsorption, due to the difference in electronegativity, all the metal adatoms donated a fraction of their electronic charges to the SiC7 sheet. Each partially charged metal center on the SiC(7)sheets could bind a maximum of 4 to 5 H-2 molecules. A high H-2 gravimetric density was achieved for several dopants at a doping concentration of 12.50%. The H-2 binding energies were found to fall within the ideal range of 0.2-0.6 eV. Based on these findings, we propose that metal-doped SiC7 sheets can operate as efficient H-2 storage media under ambient conditions.

Keywords
clean energy, functionalization, binding characteristics, dopants
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-364506 (URN)10.1007/s12274-017-1954-z (DOI)000440731800027 ()
Funder
Swedish Research CouncilStandUpSwedish Energy AgencySwedish Institute
Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2018-11-05Bibliographically approved
Tsuppayakorn-aek, P., Luo, W., Watcharatharapong, T., Ahuja, R. & Bovornratanaraks, T. (2018). Structural prediction of host-guest structure in lithium at high pressure. Scientific Reports, 8, Article ID 5278.
Open this publication in new window or tab >>Structural prediction of host-guest structure in lithium at high pressure
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 5278Article in journal (Refereed) Published
Abstract [en]

Ab initio random structure searching (AIRSS) technique is used to identify the high-pressure phases of lithium (Li). We proposed the transition mechanism from the fcc to host-guest (HG) structures at finite temperature and high pressure. This complex structural phase transformation has been calculated using ab initio lattice dynamics with finite displacement method which confirms the dynamical harmonic stabilization of the HG structure. The electron distribution between the host-host atoms has also been investigated by electron localization function (ELF). The strongly localized electron of p bond has led to the stability of the HG structure. This remarkable result put the HG structure to be a common high-pressure structure among alkali metals.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-354349 (URN)10.1038/s41598-018-23473-5 (DOI)000428367600009 ()29588486 (PubMedID)
Funder
Swedish Research Council
Available from: 2018-06-28 Created: 2018-06-28 Last updated: 2018-06-28Bibliographically approved
Tsuppayakorn-aek, P., Luo, W., Ahuja, R. & Bovornratanaraks, T. (2018). The High-Pressure Superconducting Phase of Arsenic. Scientific Reports, 8, Article ID 3026.
Open this publication in new window or tab >>The High-Pressure Superconducting Phase of Arsenic
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 3026Article in journal (Refereed) Published
Abstract [en]

Ab initio random structure searching (AIRSS) technique is predicted a stable structure of arsenic (As). We find that the body-centered tetragonal (bct) structure with spacegroup I4(1)/acd to be the stable structure at high pressure. Our calculation suggests transition sequence from the simple cubic (sc) structure transforms into the host-guest (HG) structure at 41 GPa and then into the bct structure at 81 GPa. The bct structure has been calculated using ab initio lattice dynamics with finite displacement method confirm the stability at high pressure. The spectral function alpha F-2 of the bct structure is higher than those of the body-centered cubic (bcc) structure. It is worth noting that both bct and bcc structures share the remarkable similarity of structural and property. Here we have reported the prediction of temperature superconductivity of the bct structure, with a T-c of 4.2 K at 150 GPa.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-348108 (URN)10.1038/s41598-018-20088-8 (DOI)000424985800064 ()29445106 (PubMedID)
Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-04-11Bibliographically approved
Tsuppayakorn-aek, P., Luo, W., Pungtrakoon, W., Chuenkingkeaw, K., Kaewmaraya, T., Ahuja, R. & Bovornratanaraks, T. (2018). The ideal commensurate value of Sc and the superconducting phase under high pressure. Journal of Applied Physics, 124(22), Article ID 225901.
Open this publication in new window or tab >>The ideal commensurate value of Sc and the superconducting phase under high pressure
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2018 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 124, no 22, article id 225901Article in journal (Refereed) Published
Abstract [en]

The host-guest structure of scandium is described as being built of two penetrating substructures with the incommensurate periods of the channels along the c axis. We present the ideal commensurate value of 4/3 in Sc-II using ab initio calculations. We reveal that the 3c(H) and 4c(G) structures do interpenetrate and combine to the commensurate value of 4/3 of Sc-II at a pressure of 70 GPa. Ab initio molecular dynamics confirms the stability of the commensurate value 4/3 of the host-guest structure at 300 K and 72 GPa. The pressure-induced structural phase transitions in scandium under high pressure up to 200 GPa are investigated. We use ab initio random structure searching to predict the crystal structure of Sc-III: it is the tetragonal structure with space group P4(1)2(1)2. Our calculations show that superconductivity arises in the P4(1)2(1)2 structure. This high pressure structure is not only a superconducting phase but also has been reported for the first time in this group of elements.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-372926 (URN)10.1063/1.5047251 (DOI)000453254000032 ()
Funder
Swedish Research CouncilSwedish Research Council
Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-01-10Bibliographically approved
Sun, W., Luo, W., Feng, Q. & Ahuja, R. (2017). Anisotropic distortion and Lifshitz transition in alpha-Hf under pressure. Physical Review B, 95(11), Article ID 115130.
Open this publication in new window or tab >>Anisotropic distortion and Lifshitz transition in alpha-Hf under pressure
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 11, article id 115130Article in journal (Refereed) Published
Abstract [en]

In this work we report a theoretical investigation on behavior of the elastic constant C-44 and the transverse optical phonon mode E(2)g of a-Hf under pressure within the density functional theory. In contrast to many other reported transition metals, the above two quantities do not show a synchronous relation as pressure increases. Below 13 GPa, an opposite shifting tendency has been observed. However, once the pressure is raised above 13 GPa, the trend is pulled back to be consistent. This anomalous behavior is figured out to be caused by the large lattice anisotropy of the c/a ratio along with the elastic anisotropy. The synchronous behavior is found to be in accordance with the behavior of c/a ratio with increased pressure. In our band-structure investigations the electronic topological transition has been discovered at 10 GPa, which relates to the change of c/a ratio suggested by recent literature. The presence of the Van Hove singularity shown in the densities of states has been identified and regarded as the origin of the variation of C-44 and E(2)g.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-320218 (URN)10.1103/PhysRevB.95.115130 (DOI)000396273400004 ()
Funder
Swedish Research Council
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2017-11-29Bibliographically approved
Naqvi, S. R., Hussain, T., Luo, W. & Ahuja, R. (2017). Exploring Doping Characteristics of Various Adatoms on Single-Layer Stanene. The Journal of Physical Chemistry C, 121(14), 7667-7676
Open this publication in new window or tab >>Exploring Doping Characteristics of Various Adatoms on Single-Layer Stanene
2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 14, p. 7667-7676Article in journal (Refereed) Published
Abstract [en]

We have performed first-principles calculations based on density functional theory to investigate the doping characteristics of 31 different adatoms on stanene monolayer, which includes the elements of alkali metals (AM), alkaline earth metals (AEM), transition metals (TMs), and groups III-VII. The most stable configurations of all the dopants have been explored by calculating and comparing binding energies of all the possible binding sites. To comment on the uniform distribution of adatoms on stanene, the adsorption energies (E-ads) of adatoms have been compared with their experimental cohesive energies (E-c,) in the bulk phase.A further comparison reveals that the binding energies of most of the studied adatoms on stanene are much stronger than other group IV monolayers. Apart from structural and binding characteristics, bond lengths, adatom adatom distance, charge-transfer mechanism, electronic properties, and work function have also been explored in pristine and doped monolayers. The strong adsorption of adatoms on stanene, tunable electronic properties, and formation of dumbbell structures in the case of AEM and TM shows that doped stanene sheets are worth further exploration.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-322817 (URN)10.1021/acs.jpcc.7b00468 (DOI)000399629000011 ()
Funder
Swedish Research CouncilStandUpCarl Tryggers foundation
Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2017-05-30Bibliographically approved
Yang, X., Li, H., Ahuja, R., Kang, T. & Luo, W. (2017). Formation and electronic properties of palladium hydrides and palladium-rhodium dihydride alloys under pressure. Scientific Reports, 7, Article ID 3520.
Open this publication in new window or tab >>Formation and electronic properties of palladium hydrides and palladium-rhodium dihydride alloys under pressure
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2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 3520Article in journal (Refereed) Published
Abstract [en]

We present the formation possibility for Pd-hydrides and Pd-Rh hydrides system by density functional theory (DFT) in high pressure upto 50 GPa. Calculation confirmed that PdH2 in face-centered cubic (fcc) structure is not stable under compression that will decomposition to fcc-PdH and H-2. But it can be formed under high pressure while the palladium is involved in the reaction. We also indicate a probably reason why PdH2 can not be synthesised in experiment due to PdH is most favourite to be formed in Pd and H-2 environment from ambient to higher pressure. With Rh doped, the Pd-Rh dihydrides are stabilized in fcc structure for 25% and 75% doping and in tetragonal structure for 50% doping, and can be formed from Pd, Rh and H-2 at high pressure. The electronic structural study on fcc type PdxRh1-xH2 indicates the electronic and structural transition from metallic to semi-metallic as Pd increased from x = 0 to 1.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-329676 (URN)10.1038/s41598-017-02617-z (DOI)000403318400074 ()28615686 (PubMedID)
Funder
Swedish InstituteSwedish Foundation for Strategic Research Swedish Research Council
Available from: 2017-09-19 Created: 2017-09-19 Last updated: 2017-09-19Bibliographically approved
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