scholarly journals Models of the interaction of metal tips with insulating surfaces

2012 ◽  
Vol 3 ◽  
pp. 329-335 ◽  
Author(s):  
Thomas Trevethan ◽  
Matthew Watkins ◽  
Alexander L Shluger
Keyword(s):  
Plane Wave ◽  
Density Functional ◽  
Metal Cluster ◽  
Density Functional Theory Calculations ◽  
Basis Sets ◽  
Constant Frequency ◽  
Force Microscopy ◽  
Insulating Surfaces ◽  
Atomic Force ◽  
Tip Model

We present the results of atomistic simulations of metallic atomic-force-microscopy tips interacting with ionic substrates, with atomic resolution. Chromium and tungsten tips are used to image the NaCl(001) and MgO(001) surfaces. The interaction of the tips with the surface is simulated by using density-functional-theory calculations employing a mixed Gaussian and plane-wave basis and cluster-tip models. In each case, the apex of the metal cluster interacts more attractively with anions in the surfaces than with cations, over the range of typical imaging distances, which leads to these sites being imaged as raised features (bright) in constant-frequency-shift images. We compare the results of the interaction of a chromium tip with the NaCl surface, with calculations employing exclusively plane-wave basis sets and a fully periodic tip model, and demonstrate that the electronic structure of the tip model employed can have a significant quantitative effect on calculated forces when the tip and surface are clearly separated.

Investigation of BMI-PF6 Ionic Liquid/Graphite Interface Using Frequency Modulation Atomic Force Microscopy

MRS Advances ◽  
2018 ◽  
Vol 3 (44) ◽  
pp. 2725-2733 ◽  
Author(s):  
Harshal P. Mungse ◽  
Takashi Ichii ◽  
Toru Utsunomiya ◽  
Hiroyuki Sugimura
Keyword(s):  
Molecular Dynamics ◽  
Atomic Force Microscopy ◽  
Frequency Modulation ◽  
Density Functional ◽  
Pyrolytic Graphite ◽  
Density Functional Theory Calculations ◽  
Quartz Tuning Fork ◽  
Dynamics Simulation ◽  
Force Microscopy ◽  
Atomic Force

ABSTRACTStructural analysis on interfaces between ionic liquids (ILs) and solid substrates is an important study for not only the basic fundamental aspects but also many technological processes. In the present work, we utilized frequency modulation atomic force microscopy (FM-AFM) based on a quartz tuning fork sensor to elucidate the structure of interface between 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) IL and highly ordered pyrolytic graphite (HOPG) surface. It was observed that this IL form solvation layers at their interface, with ∼0.5-0.57 nm thickness of each layer. We have compared our experimental results with previously reported results from molecular dynamics simulation study, and combination of classical molecular dynamics and density functional theory calculations in order to understand the IL/HOPG interface.

scholarly journals Diacetylene polymerization on a bulk insulator surface

2017 ◽  
Vol 19 (23) ◽  
pp. 15172-15176 ◽  
Author(s):  
A. Richter ◽  
V. Haapasilta ◽  
C. Venturini ◽  
R. Bechstein ◽  
A. Gourdon ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Atomic Force Microscopy ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Insulator Surface ◽  
Force Microscopy ◽  
Atomic Force ◽  
Microscopy Images

Atomic force microscopy images and density-functional theory calculations elucidate on-surface diacetylene polymerization on the bulk insulator surface of calcite.

scholarly journals Probing the Nature of Chemical Bonds by Atomic Force Microscopy

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4068
Author(s):  
Franz J. Giessibl
Keyword(s):  
Chemical Bond ◽  
Frequency Modulation ◽  
Density Functional ◽  
Materials Science ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Chemical Bonds ◽  
Force Microscopy ◽  
Atomic Force ◽  
Single Chemical

The nature of the chemical bond is important in all natural sciences, ranging from biology to chemistry, physics and materials science. The atomic force microscope (AFM) allows to put a single chemical bond on the test bench, probing its strength and angular dependence. We review experimental AFM data, covering precise studies of van-der-Waals-, covalent-, ionic-, metallic- and hydrogen bonds as well as bonds between artificial and natural atoms. Further, we discuss some of the density functional theory calculations that are related to the experimental studies of the chemical bonds. A description of frequency modulation AFM, the most precise AFM method, discusses some of the experimental challenges in measuring bonding forces. In frequency modulation AFM, forces between the tip of an oscillating cantilever change its frequency. Initially, cantilevers were made mainly from silicon. Most of the high precision measurements of bonding strengths by AFM became possible with a technology transfer from the quartz watch technology to AFM by using quartz-based cantilevers (“qPlus force sensors”), briefly described here.

scholarly journals Uncertainties in forces extracted from non-contact atomic force microscopy measurements by fitting of long-range background forces

2014 ◽  
Vol 5 ◽  
pp. 386-393 ◽  
Author(s):  
Adam Sweetman ◽  
Andrew Stannard
Keyword(s):  
Atomic Force Microscopy ◽  
Long Range ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Extrapolation Method ◽  
Atomic Scale ◽  
Site Specific ◽  
Force Microscopy ◽  
Atomic Force ◽  
Fitting Method

In principle, non-contact atomic force microscopy (NC-AFM) now readily allows for the measurement of forces with sub-nanonewton precision on the atomic scale. In practice, however, the extraction of the often desired ‘short-range’ force from the experimental observable (frequency shift) is often far from trivial. In most cases there is a significant contribution to the total tip–sample force due to non-site-specific van der Waals and electrostatic forces. Typically, the contribution from these forces must be removed before the results of the experiment can be successfully interpreted, often by comparison to density functional theory calculations. In this paper we compare the ‘on-minus-off’ method for extracting site-specific forces to a commonly used extrapolation method modelling the long-range forces using a simple power law. By examining the behaviour of the fitting method in the case of two radically different interaction potentials we show that significant uncertainties in the final extracted forces may result from use of the extrapolation method.

Wechselwirkungen in Molekülkristallen, 166 [1, 2]. Polyiod-Moleküle I2C=CI2, (IC)4S, (IC)4NH, (IC)4N-CH3 und HCI3: Strukturbestimmung nach Kristallzüchtung oder durch Dichtefunktionaltheorie-Berechnung / Interaction in Molecular Crystals, 166 [1, 2], Polyiodo Molecules I2C=CI2, (IC)4S, (IC)4 NH, (IC)4N-CH and HCI3: Structure Determination Following Crystallization or by Density Functional Theory Calculation

2001 ◽  
Vol 56 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Hans Bock ◽  
Sven Holl ◽  
Volker Krenzel
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Crystal Packing ◽  
Density Functional Theory Calculation ◽  
Density Functional Theory Calculations ◽  
Structural Data ◽  
Basis Sets ◽  
Functional Theory ◽  
Donor Acceptor ◽  
Density Functional Theory Optimization

Abstract The structures of tri-and tetraiodo-substituted carbon compounds are determined either expe­rimentally by X-Ray Structure Analysis or, because crystallization of tetraiodothiophene could not be achieved, approximated by Density Functional Theory optimization of structural data from a donor/acceptor complex. The structures show noteworthy details such as a second po­lymorph of tetraiodoethene crystallized by sublimation or herringbone crystal packing patterns of tetraiodopyrrole derivatives. All molecular geometries are discussed and compared based on relativistic density functional theory calculations with 6 -31G* basis sets including iodine pseudopotentials. They reproduce even finer structural details due to van der Waals repulsion of the bulky iodo substituents. Natural Bond Orbital (NBO) charge distributions suggest positive partial charges at all iodine centers with the strongest polarization Cδ㊀ → Iδ㊉ in HCI3, which contains well over 97% iodine.

scholarly journals Water agglomerates on Fe3O4(001)

2018 ◽  
Vol 115 (25) ◽  
pp. E5642-E5650 ◽  
Author(s):  
Matthias Meier ◽  
Jan Hulva ◽  
Zdeněk Jakub ◽  
Jiří Pavelec ◽  
Martin Setvin ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Minimum Energy ◽  
Modern Technology ◽  
Genetic Search ◽  
Force Microscopy ◽  
Atomic Force ◽  
Temperature Programmed ◽  
Partial Dissociation ◽  
Low Coverage

Determining the structure of water adsorbed on solid surfaces is a notoriously difficult task and pushes the limits of experimental and theoretical techniques. Here, we follow the evolution of water agglomerates on Fe3O4(001); a complex mineral surface relevant in both modern technology and the natural environment. Strong OH–H2O bonds drive the formation of partially dissociated water dimers at low coverage, but a surface reconstruction restricts the density of such species to one per unit cell. The dimers act as an anchor for further water molecules as the coverage increases, leading first to partially dissociated water trimers, and then to a ring-like, hydrogen-bonded network that covers the entire surface. Unraveling this complexity requires the concerted application of several state-of-the-art methods. Quantitative temperature-programmed desorption (TPD) reveals the coverage of stable structures, monochromatic X-ray photoelectron spectroscopy (XPS) shows the extent of partial dissociation, and noncontact atomic force microscopy (AFM) using a CO-functionalized tip provides a direct view of the agglomerate structure. Together, these data provide a stringent test of the minimum-energy configurations determined via a van der Waals density functional theory (DFT)-based genetic search.

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