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Wei Hu

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Wei Hu
Postdoctoral Researcher
Computational Research Division
Phone: +1 510 541 6034
Lawrence Berkeley National Laboratory
1 Cyclotron Rd, MS 50A-3121
Berkeley, CA 94720 US

Biographical Sketch

Wei Hu is a postdoctoral fellow in the Scalable Solvers Group of the Computational Research Division. Wei Hu will help develop new software called, Discontinuous Galerkin Method for Density Functional Theory (DGDFT). The project is supported by the Department of Energy’s Scientific Discovery Through Advanced Computing (SciDAC) program.

Journal Articles

A. S. Banerjee, L. Lin, W. Hu, C. Yang and J. E. Pask, "Chebyshev polynomial filtered subspace iteration in the discontinuous Galerkin method for large-scale electronic structure calculations", Journal of Chemical Physics, October 1, 2016,

Wei Hu,  Lin Lin, Chao Yang, Jun Dai and Jinlong Yang, "Edge-Modi ed Phosphorene Nano ake Heterojunctions as Highly Ecient Solar Cells", Nano Lett, February 5, 2016, 16:1675–1682, doi: 10.1021/acs.nanolett.5b04593

Wei Hu, Lin Lin and Chao Yang, "Edge reconstruction in armchair phosphorene nanoribbons revealed by discontinuous Galerkin density functional theory", Phys. Chem. Chem. Phys., 2015, Advance Article, February 11, 2015, doi: 10.1039/C5CP00333D

With the help of our recently developed massively parallel DGDFT (Discontinuous Galerkin Density Functional Theory) methodology, we perform large-scale Kohn–Sham density functional theory calculations on phosphorene nanoribbons with armchair edges (ACPNRs) containing a few thousands to ten thousand atoms. The use of DGDFT allows us to systematically achieve a conventional plane wave basis set type of accuracy, but with a much smaller number (about 15) of adaptive local basis (ALB) functions per atom for this system. The relatively small number of degrees of freedom required to represent the Kohn–Sham Hamiltonian, together with the use of the pole expansion the selected inversion (PEXSI) technique that circumvents the need to diagonalize the Hamiltonian, results in a highly efficient and scalable computational scheme for analyzing the electronic structures of ACPNRs as well as their dynamics. The total wall clock time for calculating the electronic structures of large-scale ACPNRs containing 1080–10 800 atoms is only 10–25 s per self-consistent field (SCF) iteration, with accuracy fully comparable to that obtained from conventional planewave DFT calculations. For the ACPNR system, we observe that the DGDFT methodology can scale to 5000–50 000 processors. We use DGDFT based ab initio molecular dynamics (AIMD) calculations to study the thermodynamic stability of ACPNRs. Our calculations reveal that a 2 × 1 edge reconstruction appears in ACPNRs at room temperature.

Wei Hu, Lin Lin, Chao Yang and Jinlong Yang, "Electronic structure and aromaticity of large-scale hexagonal graphene nanoflakes", J. Chem. Phys. 141, 214704 (2014), December 2, 2014, 141:214704, doi: 10.1063/1.4902806

With the help of the recently developed SIESTA-PEXSI method [L. Lin, A. García, G. Huhs, and C. Yang, J. Phys.: Condens. Matter26, 305503 (2014)], we perform Kohn-Sham density functional theory calculations to study the stability and electronic structure of hydrogen passivated hexagonal graphene nanoflakes (GNFs) with up to 11 700 atoms. We find the electronic properties of GNFs, including their cohesive energy, edge formation energy, highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap, edge states, and aromaticity, depend sensitively on the type of edges (armchair graphene nanoflakes (ACGNFs) and zigzag graphene nanoflakes (ZZGNFs)), size and the number of electrons. We observe that, due to the edge-induced strain effect in ACGNFs, large-scale ACGNFs’ edge formation energydecreases as their size increases. This trend does not hold for ZZGNFs due to the presence of many edge states in ZZGNFs. We find that the energy gaps E g of GNFs all decay with respect to 1/L, where L is the size of the GNF, in a linear fashion. But as their size increases, ZZGNFs exhibit more localized edge states. We believe the presence of these states makes their gap decrease more rapidly. In particular, when L is larger than 6.40 nm, we find that ZZGNFs exhibit metallic characteristics. Furthermore, we find that the aromatic structures of GNFs appear to depend only on whether the system has 4N or 4N + 2 electrons, where N is an integer.

Wenqi Xia, Wei Hu, Zhenyu Li and Jinlong Yang, "A first-principles study of gas adsorption on germanene", Phys. Chem. Chem. Phys., 2014,16, 22495-22498, August 29, 2014, doi: 10.1039/C4CP03292F

The adsorption of common gas molecules (N2, CO, CO2, H2O, NH3, NO, NO2, and O2) on germanene is studied with density functional theory. The results show that N2, CO, CO2, and H2O are physisorbed on germanene via van der Waals interactions, while NH3, NO, NO2, and O2 are chemisorbed on germanene via strong covalent (Ge–N or Ge–O) bonds. The chemisorption of gas molecules on germanene opens a band gap at the Dirac point of germanene. NO2 chemisorption on germanene shows strong hole doping in germanene. O2 is easily dissociated on germanene at room temperature. Different adsorption behaviors of common gas molecules on germanene provide a feasible way to exploit chemically modified germanene.

Wei Hu, Nan Xia, Xiaojun Wu, Zhenyu Li and Jinlong Yang, "Silicene as a highly sensitive molecule sensor for NH3, NO and NO2", Phys. Chem. Chem. Phys., 2014,16, 6957-6962, January 23, 2014, doi: 10.1039/C3CP55250K

On the basis of first-principles calculations, we demonstrate the potential application of silicene as a highly sensitive molecule sensor for NH3, NO, and NO2 molecules. NH3, NO and NO2 molecules chemically adsorb on silicene via strong chemical bonds. With distinct charge transfer from silicene to molecules, silicene and chemisorbed molecules form charge-transfer complexes. The adsorption energy and charge transfer in NO2-adsorbed silicene are larger than those of NH3- and NO-adsorbed silicones. Depending on the adsorbate types and concentrations, the silicene-based charge-transfer complexes exhibit versatile electronic properties with tunable band gap opening at the Dirac point of silicene. The calculated charge carrier concentrations of NO2-chemisorbed silicene are 3 orders of magnitude larger than intrinsic charge carrier concentration of graphene at room temperature. The results present a great potential of silicene for application as a highly sensitive molecule sensor.

Wei Hu, Zhenyu Li and Jinlong Yang, "Structural, electronic, and optical properties of hybrid silicene and graphene nanocomposite", J. Chem. Phys. 139, 154704 (2013), October 16, 2013, doi: 10.1063/1.4824887

Structural, electronic, and optical properties of hybrid silicene and graphene (S/G) nanocomposite are examined with density functional theory calculations. It turns out that weak van der Waals interactions dominate between silicene and graphene with their intrinsic electronic properties preserved. Interestingly, interlayer interactions in hybrid S/G nanocomposite induce tunable p-type and n-type doping of silicene and graphene, respectively, showing their doping carrier concentrations can be modulated by their interfacial spacing.

Wei Hu, Zhenyu Li and Jinlong Yang, "Surface and size effects on the charge state of NV center in nanodiamonds", Computational and Theoretical Chemistry, 2013, 1021, 49-53, October 1, 2013, doi: 10.1016/j.comptc.2013.06.015

Electronic structures and stability of nitrogen–vacancy (NV) centers doped in nanodiamonds (NDs) have been investigated with large-scale density functional theory (DFT) calculations. Spin polarized defect states are not affected by the particle sizes and surface decorations, while the band gap is sensitive to these effects. Induced by the spherical surface electric dipole layer, surface functionalization has a long-ranged impact on the stability of charged NV centers doped in NDs. NV− center doped in DNs is more favorable for n-type fluorinated diamond, while NV0 is preferred for p-type hydrogenated NDs. Therefore, surface decoration provides a useful way for defect state engineering.

Wei Hu, Xiaojun Wu, Zhenyu Li and Jinlong Yang, "Helium separation via porous silicene based ultimate membrane", Nanoscale, 2013, 5, 9062-9066, July 11, 2013, doi: 10.1039/C3NR02326E

Helium purification has become more important for increasing demands in scientific and industrial applications. In this work, we demonstrated that the porous silicene can be used as an effective ultimate membrane for helium purification on the basis of first-principles calculations. Prinstine silicene monolayer is impermeable to helium gas with a high penetration energy barrier (1.66 eV). However, porous silicene with either Stone–Wales (SW) or divacancy (555[thin space (1/6-em)]777 or 585) defect presents a surmountable barrier for helium (0.33 to 0.78 eV) but formidable for Ne, Ar, and other gas molecules. In particular, the porous silicene with divacancy defects shows high selectivity for He/Ne and He/Ar, superior to graphene, polyphenylene, and traditional membranes.

Wei Hu, Zhenyu Li and Jinlong Yang, "Electronic and optical properties of graphene and graphitic ZnO nanocomposite structures", J. Chem. Phys. 138, 124706 (2013), March 28, 2013, doi: 10.1063/1.4796602

Electronic and optical properties of graphene and graphitic ZnO (G/g-ZnO) nanocomposites have been investigated with density functional theory. Graphene interacts overall weakly with g-ZnO monolayer via van der Waals interaction. There is no charge transfer between the graphene and g-ZnO monolayer, while a charge redistribution does happen within the graphene layer itself, forming well-defined electron-hole puddles. When Al or Li is doped in the g-ZnO monolayer, substantial electron (n-type) and hole (p-type) doping can be induced in graphene, leading to well-separated electron-hole pairs at their interfaces. Improved optical properties in graphene/g-ZnO nanocomposite systems are also observed, with potential photocatalytic and photovoltaic applications.

Wei Hu, Xiaojun Wu, Zhenyu Li and Jinlong Yang, "Porous silicene as a hydrogen purification membrane", Phys. Chem. Chem. Phys., 2013, 15, 5753-5757, February 22, 2013, doi: 10.1039/C3CP00066D

We investigated theoretically the hydrogen permeability and selectivity of a porous silicene membrane via first-principles calculations. The subnanometer pores of the silicene membrane are designed as divacancy defects with octagonal and pentagonal rings (585-divacancy). The porous silicene exhibits high selectivity comparable with graphene-based membranes for hydrogen over various gas molecules (N2, CO, CO2, CH4, and H2O). The divacancy defects in silicene are chemically inert to the considered gas molecules. Our results suggest that the porous silicene membrane is expected to find great potential in gas separation and filtering applications.

Wei Hu, Zhenyu Li and Jinlong Yang, "Diamond as an inert substrate of graphene", J. Chem. Phys. 138, 054701 (2013), February 1, 2013, doi: 10.1063/1.4789420

Interaction between graphene and semiconducting diamond substrate has been examined with large-scale density functional theory calculations. Clean and hydrogenated diamond (100) and (111) surfaces have been studied. It turns out that weak van der Waals interactions dominate for graphene on all these surfaces. High carrier mobility of graphene is almost not affected, except for a negligible energy gap opening at the Dirac point. No charge transfer between graphene and diamond (100) surfaces is detected, while different charge-transfer complexes are formed between graphene and diamond (111) surfaces, inducing either p-type or n-type doping on graphene. Therefore, diamond can be used as an excellent substrate of graphene, which almost keeps its electronic structures at the same time providing the flexibility of charge doping.

Wei Hu, Zhenyu Li, Jinlong Yang and Jianguo Hou, "Nondecaying long range effect of surface decoration on the charge state of NV center in diamond", J. Chem. Phys. 138, 034702 (2013), January 15, 2013, doi: 10.1063/1.4775364

Erjun Kan, Wei Hu, Chuanyun Xiao, Ruifeng Lu, Kaiming Deng, Jinlong Yang and Haibin Su, "Half-Metallicity in Organic Single Porous Sheets", J. Am. Chem. Soc., 2012, 134 (13), 5718–5721, March 22, 2012, doi: 10.1021/ja210822c

The unprecedented applications of two-dimensional (2D) atomic sheets in spintronics are formidably hindered by the lack of ordered spin structures. Here we present first-principles calculations demonstrating that the recently synthesized dimethylmethylene-bridged triphenylamine (DTPA) porous sheet is a ferromagnetic half-metal and that the size of the band gap in the semiconducting channel is roughly 1 eV, which makes the DTPA sheet an ideal candidate for a spin-selective conductor. In addition, the robust half-metallicity of the 2D DTPA sheet under external strain increases the possibility of applications in nanoelectric devices. In view of the most recent experimental progress on controlled synthesis, organic porous sheets pave a practical way to achieve new spintronics.

Thesis/Dissertations

First-Principles Study of Carbon Nanomaterials, Wei Hu and Jinlong Yang, University of Science and Technology of China, July 26, 2013, doi: 10.13140/2.1.4601.6965

Others

Jinlong Yang, Hongjun Xiang, Honghui Shang, Jun Dai, Wei Hu, Zi Xiong, and Xinming Qin, ONPAS: Order-N quantum chemistry pakage for large scale ab initio simulation, Quantum Chem., 2014, December 2, 2014, doi: 10.1002/qua.24837