Simulation of Local Surface Modification in STM by ab initio Quantum Chemistry

Surface modification by means of STM has became a well-known method for the artificial formation of nanometer and atomic scale structures. The physical nature of surface modification can consist in a wide range of phenomena (from mechanical indentation up to specific tip-induced chemistry). The high electrical field at the STM tip is considered to be the main feature of STM modification experiments. The field strength is comparable with intramolecular ones and can influence the chemical bonding in surface structures. The model of STM-stimulated modification is considered using the quantum-chemical ab initio approach for a surface cluster in the high electrical field. The destabilization effect, energy level shift, and bond polarization under the STM tip field occur and can show the atomistic nature of surface transformations in STM.

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Adsorption of water in Na-LTA zeolite : an Ab Initio Molecular Dynamics investigation

Physical Chemistry Chemical Physics ◽

10.1039/d1cp02624k ◽

2021 ◽

Author(s):

Joharimanitra Randrianandraina ◽

Michael Badawi ◽

Bruno Cardey ◽

Manuel Grivet ◽

Jean-Emmanuel Groetz ◽

...

Keyword(s):

Molecular Dynamics ◽

Ab Initio ◽

Tritiated Water ◽

Atomic Scale ◽

Ab Initio Molecular Dynamics ◽

Lta Zeolite ◽

Wide Range ◽

Adsorption Processes ◽

Adsorption Of Water

The very wide range of applications of LTA zeolites, including the storage of tritiated water, implies that a detailed and accurate atomic-scale description of the adsorption processes taking place in...

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Grain boundary structure in B2 Fe-Al ordered alloys: an atomic-scale simulation

MRS Proceedings ◽

10.1557/proc-652-y8.16 ◽

2000 ◽

Vol 652 ◽

Author(s):

R. Besson ◽

C. S. Becquart ◽

A. Legris ◽

J. Morillo

Keyword(s):

Grain Boundary ◽

Ab Initio ◽

Coincidence Site Lattice ◽

Bulk Composition ◽

Atomic Scale ◽

Boundary Structure ◽

Grain Boundary Structure ◽

Symmetric Tilt ◽

Ab Initio Potentials ◽

Ab Initio Approach

ABSTRACTWe calculated the atomic structure of the (310)[001] symmetric tilt grain boundary (GB) in B2 ordered Fe-Al, using empirical and ab initio potentials. Including a proper treatment of the influence of small departures from bulk B2 stoichiometry on chemical potentials through a thermodynamic point-defect model, we obtain low energy GB variants geometrically close to the usual ones deduced from the coincidence site lattice (CSL) theory. In Al-rich alloys, both methods predict GB Al segregation whereas in Fe-rich alloys, the empirical (resp. ab initio) approach leads to Fe (resp. Fe or no) segregation. With both methods, strong GB chemical effects triggered by the bulk composition appear, showing that in B2 Fe-Al, GB properties may be strongly influenced by small bulk composition changes.

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Scanning tunneling microscopy of polymers: A status report

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153622 ◽

1989 ◽

Vol 47 ◽

pp. 330-331

Author(s):

P.E. Russell ◽

I.H. Musselman

Keyword(s):

High Resolution ◽

Scanning Tunneling Microscopy ◽

Sample Surface ◽

Atomic Scale ◽

Constant Current ◽

Scanning Tunneling ◽

Status Report ◽

Tunneling Microscopy ◽

Research Issues ◽

Wide Range

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.

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