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opencc-by-4.0Jun 2024View details →

Electrochemical on-surface synthesis of a strong electron-donating graphene nanoribbon catalyst

On-surface synthesis of edge-functionalized graphene nanoribbons (GNRs) has attracted much attention. However, producing such GNRs on a large scale through on-surface synthesis under ultra-high vacuum on thermally activated metal surfaces has been challenging. This is mainly due to decomposition of functional groups at temperatures of 300 to 500°C and limited monolayer GNR growth based on the metal catalysis. To overcome these obstacles, we developed an on-surface electrochemical technique that utilizes redox reactions of asymmetric precursors at an electric double layer where a strong electric field is confined to the liquid-solid interface. <a name="_Hlk164526696"></a>We successfully demonstrate layer-by-layer growth of strong electron-donating GNRs on electrodes at temperatures <80°C without decomposing functional groups. We show that high-voltage facilitates previously unknown heterochiral di-cationic polymerization. <a name="_Hlk164368440"></a>Electrochemically produced GNRs exhibiting one of the strongest electron-donating properties known, enable extraordinary silicon-etching catalytic activity, exceeding those of noble metals, with superior photoconductive properties. Our technique advances the possibility of producing various edge-functional GNRs.

opencc-by-4.0Jul 2024View details →

Data for: Cationic Polaron Delocalization in Porphyrin Nanoribbons

The xyz coordinates for the calculated geometries (B3LYP/6-31G*) of radical cations PN·+ for N = 1, 2, 3, 4, 6, 10, 14 and 18.

opencc-by-4.0Aug 2024View details →

Electronic Structure and Topology in Gulf-edged Zigzag Graphene Nanoribbons

<h1>Electronic Structure, Topology and Spin-Polarization in Gulf-edged Zigzag Graphene Nanoribbons</h1> This repository collects the necessary calculation files to reproduce the results shown in our manuscript (<a title="arXiv" href="https://arxiv.org/abs/2408.14839" target="_blank" rel="noopener">arXiv</a>). It includes the following parts: * A) Structure files * B) TB calculations * C) DFT calculations * D) GW calculations * E) Parametrization of TB with Hubbard-U (TB+U) * F) TB+U calculations * G) ZGNR systems  * H) Calculations for different $U$ values <h1>(A) Structure files</h1> ZGNR-G structures, created with a C-C (C-H) bond length of 1.4 Ang (1.1 Ang) and bond angles of 120°. Structures are given with and without saturation of dangling bonds by hydrogen atoms. The unit cells are rectangular. The GNR is periodic in the x-direction, and a vacuum gap of 20 Ang between the carbon atoms is added in the y- and z-direction. We did not perform geometry optimization. Files are given in XYZ, XSF, and CIF format. The structural parameters are varied in the following range: * $N$=4...11 * $a$=3...10 * $M$=2...9 (depending on $a$) * $b$=0...a/2 (depending on $a$ and whether $N$ is odd or even) * S and L inversion center The files are named in the following way:  * Carbon only (used in TB calculations): $N$-ZGNR-G$M$_$a$_$b$_<inversion center>.<file format> * Saturated systems (used in DFT calculations): $N$-ZGNR-G$M$_$a$_$b$_<inversion center>_saturated.<file format> <h1>(B) TB calculations</h1> Minimal calculation files for the complete set of structures: * Structure file in CIF format * PythTB input file (onsite energy $\alpha$=0, 1st-NN hopping element $t_1$=-1) * Calculation results in JSON format The data files contain the calculated band gaps and Z2 topological invariants, sorted into tables by structural parameters. A table is given for each combination of $N$, $M$, and inversion center. Each table varies the parameter $a$ in the rows (value of $a$ given first in each line) and the parameter $b$ in the columns (values not explicitly given, varied from 0 (0.5) to $a$/2 for even (odd) $N$). The band gaps are given in units of the 1st-NN hopping element $t_1$. The Z2 topological invariant is calculated using the Zak phase. A value is given for metallic systems even though the equations are not applicable to these systems. Additionally, the results are given as a simple list. <h1>(C) DFT calculations</h1> Calculation files for the subset of systems studied on the DFT/HSE06 level with a tight tier 1 basis and a k-grid of 18x3x3 using FHI-aims. ZGNR-G systems for this subset are selected to have a maximum of 100 carbon atoms in the primitive unit cell. Calculations are performed both without and with spin polarization. Spin-polarized systems are run with both an antiferromagnetic (AFM) and ferromagnetic (FM) initial guess (by placing an initial spin moment on the zigzag edge atoms), resulting in an AFM or FM magnetic state, respectively.  For each calculation, the following files are stored: * geometry.in: input geometry * control.in: input file for FHI-aims * aims.out: output file for FHI-aims  * band1001.out: band structure file for the first spin channel * band2001.out: band structure file for the second spin channel (only for spin-polarized calculations) * cube_001_spin_density.cube: converged spin density in CUBE format (compressed in ZIP format to save storage space after extracting calculation files) * spin-polarization.png: plot of spin moments for carbon atoms (only for spin-polarized calculations) * gap.dat: band gap, extracted from the band structure file * spin_max.dat: maximum absolute spin moment, extracted from the Mulliken projection results Additionally, for each structure, a plot comparing the band structure without spin polarization, the band structure of the AFM state, and the band structure of the FM state are stored. The DAT files are not stored for the FM state as those are never the magnetic ground state and thus were not further analyzed. In addition to the calculation files, the main results are collected in DAT files: the total energy (without spin polarization, AFM state, FM state), the band gap (without spin polarization and AFM state), and the maximum spin moment (only for the AFM state). <h1>(D) GW calculations</h1> Calculation files for the GW calculations, performed for 4-ZGNR, 5-ZGNR, and 6-ZGNR. They are calculated at the GW@PBE level and compared against calculations on the DFT/PBE and DFT/HSE06 level. Calculations are performed using FHI-aims with a tier 1 or tier 2 basis set and varying k-grids as visible from the file names. For each calculation, the input and output files are stored. They are sorted into subdirectories by their properties in the following order: * Studied system, * Method (DFT or GW), * Functional, and * Basis set and k-grid. <h1>(E) Parametrization of TB with Hubbard-U (TB+U)</h1> The parametrization of TB+U was done in two steps: (1) parametrization of the 1st NN hopping element $t_1$ and (2) the subsequent parametrization of the Hubbard-U, using the previously parametrized $t_1$. <h2>(1) Parametrization of $t_1$</h2> The parametrization of $t_1$ was done using the ZGNR-G systems available for DFT calculations. The TB and DFT calculations without spin polarization were used from steps B and C. Systems were excluded from the data set if the position of the DFT band gap was not reproduced in TB, leaving 372 ZGNR-G systems in the data set. The parametrization itself was done by linear regression of the DFT band gap in eV as a function of the TB band gap in units of $t_1$, resulting in y=3.328x-0.072 (R^2=0.951), giving $t_1$=3.328 eV. The TB and DFT band gaps are stored in the file "step1_parametrize_t1.dat"; the calculation files are taken directly from steps B and C. <h2>(2) Parameterization of $U$</h2> The parameterization of the Hubbard-U was done by first running TB+U calculations with different $U$ values. For this purpose, we varied $U$ from 0 to 5 in intervals of 0.2, using $t_1$=-1 to keep this step independent of the parametrization of $t_1$. The resulting band gaps are stored in DAT files in the subdirectory "calc_step2_variation_U" with a single file per ZGNR-G system. To save storage space, we did not upload further calculation files - the input files are equivalent to those uploaded in step F, just with different values for $t_1$ and $U$.  Afterward, we used these results to obtain the optimal $U$ value for each system, focusing on systems that show a band gap opening in the AFM state on the DFT/HSE06 level. We performed the parametrization by identifying which value of $U$ in each system gives the best agreement of the TB+U band gap with the DFT band gap in the AFM state, using the calculations from step C and interpolating linearly between the $U$ values of the scan described above. We then ran a TB+U calculation with the obtained $U$ value to check the agreement with the DFT calculations. We generally obtained good agreement with a few exceptions that were filtered out: systems that resulted in a $U$ of zero and those without a band gap opening in the AFM state of the TB+U calculation. The results of the remaining 414 ZGNR-G systems are summarized in "step2_parametrize_U.dat". The final value of $U$ was obtained by averaging over those systems, yielding an average of 1.720 $t_1$, equivalent to 5.723 eV. The calculation files used for parametrization, including those filtered out, are stored in "calc_step2_TB+U_calculations". Plots comparing the band structures on DFT/HSE06 level, TB, and TB+U are in "plots_step2_fit_agreement". <h1>(F) TB+U calculations</h1> Calculation files for the complete set of structures: * Structure file in XYZ format * PythTB input file (onsite energy $\alpha$=0, 1st-NN hopping element $t_1$=-1, $U$=1.72 $t_1$) * Calculation results in JSON format * Plot of the band structure from TB vs. TB+U (AFM state) * Plot of spin moments as an overlay over the atomic structure The data files contain the band gaps on TB and TB+U level ("results_band_gaps.dat"), the position of VBM and CBM on TB and TB+U level ("results_band_edge_positions.dat"), and spin momentum quantities ("results_spin_moments.dat"). Please note that, compared to the JSON files, a factor of 2 is applied to obtain the spin moment; this corrects the PythTB calculations, which multiply the final spin-polarization by a factor of 1/2 to account for electrons being particles with spin 1/2. <h1>(G) ZGNR systems</h1> ZGNR systems without gulf edges are included in the data set as a reference system. Structures are included in the subdirectory "structures" with widths $N$ from 2 to 50, analogously to part A. For all ZGNRs, DFT and TB+U calculations were performed. The provided files are equivalent to parts C and F. Additionally, for the DFT calculations with spin polarization, files for the maximum, minimum, and average (over the carbon atoms) spin moments are provided, distinguished by results from Mulliken and Hirshfeld analysis. The plots of the spin moments are also given for both the Mulliken and Hirshfeld analysis results. The data files contain the band gaps of the AFM state on DFT and TB+U level ("results_band_gaps_AFM_state.dat"), the total energy of the DFT calculations without and with spin-polarization in the AFM and FM state ("results_total_energies_DFT.dat"), as well as the maximum, minimum, and average (averaged over the C atoms) spin moment of the TB+U and DFT calculations, distinguished by Mulliken and Hirshfeld analysis ("results_spin-moments_maximum.dat," "results_spin-moments_minimum.dat," "results_spin-moments_average.dat"). Please note that, compared to the JSON files, a factor of 2 is applied to obtain the spin moment for the TB+U calculations. <h1>(H) Calculations for different $U$ values</h1> TB+U calculations similar to part F were performed for ZGNR and ZGNR-G systems. The main difference is that different values of $U$ were used: 1.20, 1.50, 1.72, and 2.00 in units of $t_1$. Please note that, compared to the JSON files, a factor of 2 is applied to obtain the spin moment for the TB+U calculations.

opencc-by-4.0Oct 2022View details →

Structure-imposed electronic topology in cove-edged graphene nanoribbons

Abstract In cove-edged zigzag graphene nanoribbons (ZGNR-C), one terminal group per length unit is removed on each zigzag edge, forming a regular pattern of coves which controls their electronic structure. Based on three structural parameters that unambiguously characterize the atomistic structure of ZGNR-C, we present a scheme that classifies their electronic state, i.e., if they are metallic, topological insulators or trivial semiconductors, for all possible widths N, unit lengths a and cove position offsets at both edges b, thus showing the direct structure-electronic structure relation. We further present an empirical formula to estimate the band gap of the semiconducting ribbons from N,a, and b. Finally, we identify all geometrically possible ribbon terminations and provide rules to construct ZGNR-C with well-defined electronic structure. DOI: 10.1103/PhysRevLett.129.216401 Content of repository The repository contains the inputs and outputs of tight-binding (TB) calculations of ZGNR-C based on <a href="http://www.physics.rutgers.edu/pythtb/">PythTB</a>. For each analysed structure one subdirectory is created, labelled as "N-ZGNR-C_a_b_inv_cell$\alpha$_termination". This corresponds to a N-ZGNR-C(a,b) with inversion center at the unit cell boundary S or L ("inv"), unit cell angle $\alpha$ ("cell$\alpha$": 60°, 90°, or 120°) and a given unit cell termination (armchair, zigzag or bearded). Each directory contains the atomic structure in xsf and cif format, the PythTB input file, the output as a json file, and the calculated band structure as image file. The json file contains the band structure information (path and eigenvalues), the raw Zak phase in units of $\pi$ without modulo 2, and the final $\mathbb{Z}_2$ invariant.

opencc-by-4.0Oct 2023View details →

Atomically Precise Incorporation of BN-Doped Rubicene into Graphene Nanoribbons

Raw file of publication entitled "Atomically Precise Incorporation of BN-Doped Rubicene into Graphene Nanoribbons"https://doi.org/10.1021/acs.jpcc.2c05866

opencc-zeroDec 2023View details →

Adsorption of N, He, and Ne on CGe nanoribbons for sensing and optoelectronic applications

Research into nanomaterials yields numerous exceptional applications in contemporary science and technology. The subject of this investigation is a one-dimensional nanostructure, six atoms wide, featuring hydrogen-functionalized edges. The theoretical foundation of this study relies on Density Functional Theory (DFT) and is executed through the utilization of the Vienna Ab initio Simulation Package (VASP). The outcomes demonstrate the stability of adsorption configurations, along with the preservation of the hexagonal honeycomb lattice. The pristine configuration, characterized by a wide bandgap, is well-suited for optoelectronic applications, whereas adsorption configurations find their application in gas sensing. Nitrogen (N) adsorption transforms the semiconducting system into a semi-metallic one, with the spin-up state displaying semiconductor characteristics and the spin-down state exhibiting metallic attributes. The intricate multi-orbital hybridization is explored through the analysis of partial states. While the pristine system remains non-magnetic, N adsorption introduces a magnetic moment of 0.588 μB. Examination of charge density differences indicates a significant charge transfer from N to the CGe substrate surface. Optical properties are systematically investigated, encompassing the dielectric function, absorption coefficient, and electron-hole density. Notably, the real part of the dielectric function displays negative values, a result that holds promise for future communication applications.

opencc-by-4.0Nov 2024View details →

Electron beam-splitting effect with crossed zigzag graphene nanoribbons in high-spin metallic states

OPEN DATA related to the research publication:   Sofia Sanz, Géza Giedke, Daniel Sánchez-Portal, Thomas Frederiksen, Electron beam-splitting effect with crossed zigzag graphene nanoribbons in high-spin metallic states  <a href="https://doi.org/10.48550/arXiv.2408.08787">[arXiv:2408.08787]</a> ABSTRACT: Here we analyze the electron transport properties of a device formed of two crossed graphene nanoribbons with zigzag edges (ZGNRs) in a spin state with total magnetization different from zero. While the ground state of ZGNRs has been shown to display antiferromagnetic ordering between the electrons at the edges, for wide ZGNRs--where the localized spin states at the edges are decoupled and the exchange interaction is close to zero--, in presence of relatively small magnetic fields, the ferromagnetic (FM) spin configuration can in fact become the state of lowest energy due to the Zeeman effect. In these terms, by comparing the total energy of a periodic ZGNR as a function of the magnetization per unit cell we obtain the FM-like solution of lowest energy for the perfect ribbon, the corresponding FM-like configuration of lowest energy for the four-terminal device formed of crossed ZGNRs, and the critical magnetic field needed to excite the system to this spin configuration. By performing transport calculations, we analyze the role of the distance between layers and the crossing angle of this device in the electrical conductance, at small gate voltages. The problem is approached employing the mean-field Hubbard Hamiltonian in combination with non-equilibrium Green's functions. We find that ZGNR devices subject to transverse magnetic fields may acquire a high-spin configuration that ensures a metallic response and tunable beam splitting properties, making this setting promising for studying electron quantum optics with single-electron excitations.

opencc-by-4.0Mar 2022View details →

Solution Phase Growth and Analysis of Super-thin Zigzag Tin Selenide Nanoribbons

Tin selenide (SnSe), a highly promising layered material, has been garnering particular interest in recent times due to its significant promise for future energy devices. Herein we report a simple solution-phase approach for growing highly crystalline layered SnSe nanoribbons. Polyvinylpyrrolidone (PVP) was used as a templating agent to selectively passivates the (100) and (001) facets of the SnSe nanoribbons resulting in the unique growth of nanoribbons along their b-axis with a defined zigzag edge state along the sidewalls. The SnSe nanoribbons are few layers thick (&sim;20 layers), with mean widths of &sim;40 nm, and achievable length of >1 μm. Nanoribbons could be produced in relatively high quantities (>150 mg) in a single batch experiment. The PVP coating also offers some resistance to oxidation, with the removal of the PVP seen to lead to the formation of a SnSe/SnOx core-shell structure. The use of non-toxic PVP to replace toxic amines that are typically employed for other 1D forms of SnSe is a significant advantage for sustainable and environmentally friendly applications. Heat transport properties of the SnSe nanoribbons, derived from power-dependent Raman spectroscopy, demonstrate the potential of SnSe nanoribbons as thermoelectric material.

opencc-by-4.0Aug 2022View details →

Data for "A versatile platform for graphene nanoribbon synthesis, electronic decoupling, and spin polarized measurements"

Data for figures of the main and supplemental part of "A versatile platform for graphene nanoribbon synthesis, electronic decoupling, and spin polarized measurements" by <a href="https://doi.org/10.1039/D2NA00668E">Cahlík et al., Nanoscale Advances (2023)</a>

publicOct 2025View details →

Data from: Comprehensive first principles study on CO and NO gas adsorption effects on the structural, electronic, and optical properties of ASiSn nanoribbons

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publicDec 2023View details →

Adsorption of N, He, and Ne on CGe nanoribbons for sensing and optoelectronic applications

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