The anchoring of benzene molecules on lithium adsorption sites at the surface of graphene and nanoribbons thereof are investigated. The effects of adsorbate densities, specific adsorption locations, and spin states on the structural stability and electronic properties of the underlying graphene derivatives are revealed. At sufficiently high densities, bare lithium adsorption turns armchair graphene nanoribbons metallic and their zigzag counterparts half-metallic due to charge transfer from the adatom to the π electronic system. Upon benzene adsorption, the lithium cation encounters two π systems thus drawing charge back towards the benzene molecule. This, in turn, leads to the opening of a measurable bandgap, whose size and character are sensitive to the adsorbate density, thus indicating that a chemical detector based on lithium adsorbed graphene may be devised. Our results are therefore expected to support the design of novel graphene-based sensing and switching devices.
Hydrocarbon tribopolymer, a type of polymer formed due to friction between surfaces, is a major impediment to the development of micro- and nanoelectromechanical systems (MEMS/NEMS) devices for industrial application. Tribopolymer buildup can prevent MEMS and NEMS from making or breaking electrical contact. We describe the adsorption of benzene (C6H6) on the RuO2(110) surface using density functional theory. This adsorption is an important initial step in the mechanism of hydrocarbon tribopolymer layer formation on MEMS and NEMS devices. The adsorption interaction is studied by considering thr…
Adsorption of benzene, phenol, propane and carbonic acid molecules on oxidized Al(111) and alpha-Al2O3(0001) surfaces: A first-principles study
我们提出的从头计算的结果描述了某些小的有机分子在清洁和氧化的Al（111）表面以及在α-Al 2 O 3（0001）表面的吸附。结果表明，苯在清洁和氧化的Al（111）表面上的吸附一般较弱，吸附能最大为-0.5eV/苯分子，且吸附在离表面相当远的地方。吸附能在不同的吸附位点和作为氧覆盖度的函数变化很弱。对于氧化铝表面，我们发现没有苯吸附在所有。我们还计算了铝和氧化铝表面上的苯酚分子，因为它与苯分子相似。结果表明，苯酚在氧化铝表面上有弱吸附，而在铝或氧化铝表面上没有吸附。对于丙烷分子，在氧化的铝或氧化铝表面上都没有吸附，而碳酸分子强烈地结合到氧化铝上，但不结合到铝表面上。
The adsorption of benzene on the Si(100) surface is studied theoretically using the self-consistent van der Waals density functional (vdW-DF) method. The adsorption energies of two competing adsorption structures, butterfly (BF) and tight-bridge (TB) structures, are calculated with several vdW-DFs at saturation coverage. Our results show that recently proposed vdW-DFs with high accuracy all prefer TB to BF, in accord with more accurate calculations based on exact exchange and correlation within the random phase approximation. Detailed analyses reveal the important roles played by the molecule-…
Application of van der Waals Density Functional to an Extended System: Adsorption of Benzene and Naphthalene on Graphite
它表明，它现在是可能的，包括范德华相互作用，通过非经验的实施密度泛函理论来描述在电子结构计算中的相关能无限系统的没有特定的对称性。vdW-DF泛函[Phys. Rev. Lett. 92，246401（2004）]应用于苯和萘在无限石墨片上的吸附，以及两个石墨片之间的结合。与最近的热脱附数据[Phys.Rev.B69，535406（2004）]的比较显示了vdW-DF方法的巨大前景。
Using a van der Waals density functional (vdW-DF) [Phys. Rev. Lett. 92, 246401 (2004)], we perform ab initio calculations for the adsorption energy of benzene (Bz) on Cu(111) as a function of lateral position and height. We find that the vdW-DF inclusion of nonlocal correlations (responsible for dispersive interactions) changes the relative stability of eight binding-position options and increases the binding energy by over an order of magnitude, achieving good agreement with experiment. The admolecules can move almost freely along a honeycomb web of "corridors" passing between fcc and hcp hol…
We have studied the adsorption of Li atoms at the hollow sites of graphene nanoribbons (zigzag and armchair), graphene, and fullerenes by means of density functional theory calculations including local and semilocal functionals. The binding energy of a Li atom on armchair nanoribbons (of about 1.70 eV for LSDA and 1.20 eV for PBE) is comparable to the corresponding value in graphene (1.55 and 1.04 eV for LSDA and PBE, respectively). Notably, the interaction between Li and zigzag nanoribbons is much stronger. The binding energy of Li at the edges of zigzag nanoribbons is about 50% stronger than…
Exploring the role of van der Waals (vdW) forces on the adsorption of molecules on extended metal surfaces has become possible in recent years thanks to exciting developments in density functional theory (DFT). Among these newly developed vdW-inclusive methods, interatomic vdW approaches that account for the nonlocal screening within the bulk [V. G. Ruiz, W. Liu, E. Zojer, M. Scheffler, and A. Tkatchenko, Phys. Rev. Lett. 108, 146103 (2012)] and improved nonlocal functionals [J. Klimes, D. R. Bowler, and A. Michaelides, J. Phys.: Condens. Matter 22, 022201(2010)] have emerged as promising cand…
The adsorption of aromatic molecules on metal surfaces plays a key role in condensed matter physics and functional materials. Depending on the strength of the interaction between the molecule and the surface, the binding is typically classified as either physisorption or chemisorption. Van der Waals (vdW) interactions contribute significantly to the binding in physisorbed systems, but the role of the vdW energy in chemisorbed systems remains unclear. Here we study the interaction of benzene with the (111) surface of transition metals, ranging from weak adsorption (Ag and Au) to strong adsorpti…
The adsorption of benzene and C60 on graphene and boron nitride (BN) is studied using density functional theory with the non-local correlation functional vdW-DF. By comparing these systems we can systematically investigate their adsorption nature and differences between the two functional versions vdW-DF1 and vdW-DF2. The bigger size of the C60 molecule makes it bind stronger to the surface than benzene, yet the interface between the molecules and the sheets are similar in nature. The binding separation is more sensitive to the exchange variant used in vdW-DF than to the correlation version. T…
We study numerically the adsorption of a mixture of CO$_2$ and CH$_4$ on a graphite substrate covered by graphene nanoribbons (NRs). The NRs are flat and parallel to the graphite surface, at a variable distance ranging from 6 Å to 14 Å. We show that the NRs-graphite substrate acts as an effective filter for CO$_2$. Our study is based on Molecular Dynamics (MD) simulations. Methane is considered a spherical molecule, and carbon dioxide is represented as a linear rigid body. Graphite is modeled as a continuous material, while the NRs are approached atomistically. We observe that when the NRs are…
First-principles and semi-empirical tight binding calculations were performed to understand the adsorption of oxygen on the surface of two dimensional (2D) and zigzag stanene nano-ribbons. The intrinsic spin-orbit interaction is considered in the Kane-Mele tight binding model. The adsorption of an oxygen atom or molecule on the 2D stanene opens an electronic energy band gap. We investigate the helical edge states and topological phase in the pure zigzag stanene nano-ribbons. The adsorption of oxygen atoms on the zigzag stanene nano-ribbons deforms the helical edge states at the Fermi level whi…
Graphene nanoribbons (GNRs) are ultra-narrow strips of graphene that have the potential to be used in high-performance graphene-based semiconductor electronics. However, controlled growth of GNRs on dielectric substrates remains a challenge. Here, we report the successful growth of GNRs directly on hexagonal boron nitride substrates with smooth edges and controllable widths using chemical vapour deposition. The approach is based on a type of template growth that allows for the in-plane epitaxy of mono-layered GNRs in nano-trenches on hexagonal boron nitride with edges following a zigzag direct…
Magnetic properties of quasi one-dimensional vanadium-benzene nanowires (VBNW) are investigated theoretically with the absorption of gas molecules-NO and NO2. With the increase adsorption of NO on VBNW, the phase transition from half metal to ferromagnetic metal and last to paramagnetic semiconductor can be observed. With the increase of NO2 on VBNW, half metallic property can be enhanced at first and decreased later. Thus, the electronic and magnetic properties of VBNW can be sensitive and selective to NO and NO2, revealing the potential applications in spintronic sensors of these two kinds o…
We show by first-principles calculations that the electronic properties of zigzag graphene nanoribbons (Z-GNRs) adsorbed on Si(001) substrate strongly depend on ribbon width and adsorption orientation. Only narrow Z-GNRs with even rows of zigzag chains across their width adsorbed perpendicularly to the Si dimer rows possess an energy gap, while wider Z-GNRs are metallic due to width-dependent interface hybridization. The Z-GNRs can be metastably adsorbed parallel to the Si dimer rows, but show uniform metallic nature independent of ribbon width due to adsorption induced dangling-bond states on…
Interfacial Coupling and Sparse Intercalation of 7-Atom-Wide Armchair Graphene Nanoribbons by N-Heterocyclic Carbene Monolayers
Empa - Swiss Federal Laboratories for Materials Science and Technology（瑞士联邦材料科学与技术研究院）；Max Planck Institute of Microstructure Physics（马克斯·普朗克微观结构物理研究所）；Technische Universität Dresden（德累斯顿工业大学）；University of Chinese Academy of Science（中国科学院大学）
The dramatic changes in electronic and magnetic properties are investigated using the first-principles calculations for (Cl, Br, I, At)-adsorbed graphene nanoribbons. The rich and unique features are clearly revealed in the adatom-dominated band structures, p-type doping, spin arrangement/magnetic moment, spatial charge distribution, and orbital- and spin-projected density of states. Halogen adsorptions can create the non-magnetic, ferromagnetic or anti-ferromagnetic metals, being mainly determined by concentrations and edge structures. The number of holes per unit cell increases with the adat…
Based on atomistic simulations, the nonlinear elastic properties of monolayer graphene nanoribbons under quasistatic uniaxial tension are predicted, emphasizing the effect of edge structures (armchair and zigzag, without and with hydrogen passivation). The results of atomistic simulations are interpreted within a theoretical framework of thermodynamics, which enables determination of the nonlinear functions for the strain-dependent edge energy and the hydrogen adsorption energy, for both zigzag and armchair edges. Due to the edge effects, the initial Young's modulus of graphene nanoribbons und…
Adsorption of eight organic molecules (acetone, acetonitrile, ammonia, benzene, methane, methanol, ethanol, and toluene) onto silicene has been investigated using van der Waals density functional theory calculations (DFT-D). The calculated values of the adsorption energies vary from $-0.11$ eV to $-0.95$ eV. Quantitatively, these values are higher than the corresponding adsorption energies of the molecules adsorbed on graphene. In addition, electronic structure calculations have been performed. The obtained values of the band gap range from 0.006 eV to 0.35 eV for acetonitrile to acetone, resp…
Pristine graphene interacts relatively weakly with Al, which is a specie of importance for novel generations of metal-ion batteries. We employ DFT calculations to explore the possibility of enhancing Al interaction with graphene. We investigate non-doped and N-doped graphene nanoribbons, address the impact of the edge sites, which are always present to some extent in real samples, and N-containing defects on the material's reactivity towards Al. The results are compared to that of pristine graphene. We show that introduction of edges does not affect the energetics of Al adsorption significantl…
We study the dipole layer formed at metal-organic interfaces by means of first-principles calculations. Interface dipoles are monitored by calculating the work function change of Au, Ag, Al, Mg and Ca surfaces upon adsorption of a monolayer of PTCDA (3,4,9,10-perylene-tetra-carboxylic-di-anhydride), perylene or benzene molecules. Adsorption of PTCDA leads to pinning of the work function for a range of metal substrates. It gives interface dipoles that compensate for the difference in the clean metal work functions, leading to a nearly constant work function. In contrast, adsorption of benzene a…
Using the ab initio pseudopotential density functional method, we investigate the functionalization of halogen molecules into graphene-based nanostructures with zigzag and armchair edges. We find that halogen molecules adsorb through chemisorption on the zigzag edge carbon atoms with a binding energy of ~1-5 eV and their adsorption on a perfect zigzag edge is preferred, in sharp contrast to physisorption on the armchair edge and elsewhere where they adsorb with a binding energy of ~0.07 eV. We suggest that our findings would be utilized for an approach to the separation of zigzag graphene nano…
The adsorption geometry of 1,3,5-tris(4-mercaptophenyl)benzene (TMB) on Cu(111) is determined with high precision using two independent methods, experimentally by quantitative low energy electron diffraction (LEED-I(V)) and theoretically by dispersion corrected density functional theory (DFT-vdW). Structural refinement using both methods consistently results in similar adsorption sites and geometries. Thereby a level of confidence is reached that allows deduction of subtle structural details such as molecular deformations or relaxations of copper substrate atoms.
We show that adsorption of one lithium atom to a polyacenes, i.e. chains of linearly fused benzene rings, will cause this chain to be slightly deformed. If we adsorb a second identical atom on the opposite side of the same ring, this deformation is dramatically enhanced despite of the fact, that a symmetric configuration seems possible. We argue, that this may be due to an instability of the Jahn-Teller type possibly indeed to a Peierls instability.
We have explored the possibility of using low dimensional phosphorene based nanoscale device for the detection of nitroaromatic based explosives. In this work, we have investigated the structural, electronic, adsorption, and quantum transport properties of phosphorene nanoribbon APNR in the presence of different nitroaromatic compounds NACs using the state-of-the-art first principle density functional theory DFT calculations. Our results reveal that the adsorption of explosive molecules is far from the APNR surface, which neither affects the structure of the explosive molecule nor the APNR sur…
On-surface synthesis has recently emerged as an effective route towards the atomically precise fabrication of graphene nanoribbons of controlled topologies and widths. However, whether and to which degree structural disorder occurs in the resulting samples is a crucial issue for prospective applications that remains to be explored. Here, we experimentally identify missing benzene rings at the edges, which we name "bite" defects, as the most abundant type of disorder in armchair nanoribbons synthesized by the bottom-up approach. First, we address their density and spatial distribution on the ba…
Polymer adhesion: first-principles calculations of the adsorption of organic molecules onto Si surfaces
用密度泛函理论计算了有机分子在清洁和氢钝化的Si（001）-（2 $\times$ 1）表面上吸附的结构和能量.苯吸附在干净的硅表面上的紧桥结构被发现是稳定的和蝴蝶结构的亚稳态。碳酸H $_2$ CO $_3$和丙烷C $_3$ H $_8$在与表面接触时解离。用H原子钝化Si表面对表面性质具有显著影响。钝化的表面是非常惰性的，并且所有分子的结合能非常弱。
The selective adsorption of a corrosive gas, SO$_2$, into two microporous pillared paddle-wheel frameworks M(bdc)(ted)0.5 [M = Ni, Zn; bdc = 1,4-benzenedicarboxylate; ted = triethylenediamine] is studied by volumetric adsorption measurements and a combination of in-situ infrared spectroscopy and ab initio density functional theory (DFT) calculations. The uptake of SO$_2$ in M(bdc)(ted)0.5 at room temperature is quite significant, 9.97 mol/kg at 1.13 bar. The major adsorbed SO$_2$ molecules contributing to the isotherm measurements are characterized by stretching bands at 1326 and 1144 cm$^{-1}…
We compare the density functional theory (DFT) results on the adsorption of small aromatic molecules (benzene, pyridine and thiophene) on gold surfaces obtained by using three types of van der Waals exchange-correlation functionals and localized basis set calculations. We show that the value of the molecule surface binding energy depends on the interplay between the BSSE effect and the tendency of the exchange-correlation functionals to overestimate both the molecule-surface as well as the gold-gold distances within the relaxed systems. Consequently, we find that by using different types of LC…
Hydrogen Storage on Transition-Metal-Decorated Nitrogen-Modified Carbon Nanoribbons
University of New England（新英格兰大学）；Karpagam Academy of Higher Education（卡尔帕甘高等教育学院）；Bhabha Atomic Research Centre（巴哈原子研究中心）；Homi Bhabha National Institute（霍米·巴巴国立研究所）；University of Canberra（堪培拉大学）；The University of Queensland（昆士兰大学）
Recently, porphyrin units have been attached to graphene nanoribbons (Por-GNR) enabling a multitude of possible structures. Here we report first principles calculations of two prototypical, experimentally feasible, Por-GNR hybrids, one of which displays a small band gap relevant for its use as electrode in a device. Embedding a Fe atom in the porphyrin causes spin polarization with a spin ground state $S=1$. We employ density functional theory and nonequilibrium Green's function transport calculations to examine a 2-terminal setup involving one Fe-Por-GNR between two metal-free, small band gap…
With a view towards optimizing gas storage and separation in crystalline and disordered nanoporous carbon-based materials, we use ab initio density functional theory calculations to explore the effect of chemical functionalization on gas binding to exposed edges within model carbon nanostructures. We test the geometry, energetics, and charge distribution of in-plane and out-of-plane binding of CO2 and CH4 to model zigzag graphene nanoribbons edge-functionalized with COOH, OH, NH2, H2PO3, NO2, and CH3. Although different choices for the exchange-correlation functional lead to a spread of values…
Adsorption sites of molecules critically determine the electric/photonic properties and its stability of heterogeneous molecule-metal interfaces. Then, selectivity of adsorption site is essential for development of the fields including organic electronics, catalysis, and biology. However, due to current technical limitations, site-selectivity remains a major challenge because of difficulty in precise selection of meaningful one among the sites. Here, we report the single site-selection at a single-molecule junction by performing newly developed hybrid technique: simultaneous characterization o…
Tribopolymer formed on the contacts of microelectromechanical and nanoelectromechanical system (MEMS/NEMS) devices is a major concern hampering their practical use in information technology. Conductive metal oxides, such as RuO$_2$ and ReO$_3$, have been regarded as promising candidate materials for MEMS/NEMS contacts due to their conductivity, hardness, and relatively chemically inert surfaces. However, recent experimental works demonstrate that trace amounts of polymer could still form on RuO$_2$ surfaces. In this study, we demonstrate the mechanism of this class of unexpected tribopolymer f…
A type of line defect (LD) composed of alternate squares and octagons (4-8) as the basic unit is currently an experimentally available topological defect in graphene lattice, which brings some interesting modification to magnetic and electronic properties of graphene. The transitional metal (TM) adsorb on graphene with line-defect (4-8), and they show interesting and attractive structural, magnetic and electronic properties. For different TMs such as Fe, Co, Mn, Ni and V, the complex systems show different magnetic and electronic properties. The TM atoms can spontaneously adsorb at quadrangula…
Electric field enhances the electronic and diffusion properties of penta-graphene nanoribbons for application in lithium-ion batteries: a first-principles study
Lambert W Function Framework for Graphene Nanoribbon Quantum Sensing: Theory, Verification, and Multi-Modal Applications
Peaceful Society, Science and Innovation Foundation（和平社会、科学与创新基金会）；Department of Occupational Science and Occupational Therapy, Faculty of Medicine, University of British Columbia（不列颠哥伦比亚大学医学院职业科学与职业治疗系）；Faculty of Land and Food Systems, University of British Columbia（不列颠哥伦比亚大学土地与食品系统学院）；Department of Physics and Astronomy, University of Western Ontario（韦仕敦大学物理与天文系）；School of Physical Sciences, Indian Institute of Technology Mandi（印度技术学院曼迪分校物理科学学院）；Department of Physics, Indian Institute of Technology Tirupati（印度技术学院蒂鲁帕蒂分校物理系）
Multiproperty Atomistic Characterization of a Synthesized Pyrazinic Nitrogen-Doped Porous Armchair Graphene Nanoribbon
Laboratory of NanoEngineering, College of Technology, University of Brasília（巴西利亚大学技术学院纳米工程实验室）；Graduate Program in Physics, Institute of Physics, University of Brasília（巴西利亚大学物理研究所物理研究生项目）；Center for Agri-Food Science and Technology, Federal University of Campina Grande（坎皮纳格兰德联邦大学农业食品科学与技术中心）；Institute of Physics, Federal University of Rio Grande do Norte（北里奥格兰德联邦大学物理研究所）；Department of Applied Physics, Gleb Wataghin Institute of Physics, University of Campinas（坎皮纳斯大学格列布·瓦塔金物理研究所应用物理系）；Department of Electrical Engineering, College of Technology, University of Brasília（巴西利亚大学技术学院电气工程系）
