The Cambridge Structural Database (CSD) contains a complete record of all published organic and metal–organic small-molecule crystal structures. The database has been in operation for over 50 years and continues to be the primary means of sharing structural chemistry data and knowledge across disciplines. As well as structures that are made public to support scientific articles, it includes many structures published directly as CSD Communications. All structures are processed both computationally and by expert structural chemistry editors prior to entering the database. A key component of this processing is the reliable association of the chemical identity of the structure studied with the experimental data. This important step helps ensure that data is widely discoverable and readily reusable. Content is further enriched through selective inclusion of additional experimental data. Entries are available to anyone through free CSD community web services. Linking services developed and maintained by the CCDC, combined with the use of standard identifiers, facilitate discovery from other resources. Data can also be accessed through CCDC and third party software applications and through an application programming interface.

https://journals.iucr.org/b/issues/2016/02/00/bm5086/bm5086.pdf

The Cambridge Structural Database

https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

Images and force measurements taken by an atomic‐force microscope (AFM) depend greatly on the properties of the spring and tip used to probe the sample’s surface. In this article, we describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AFM tip. Our procedure uses the AFM itself and does not require additional equipment.

Calibration of atomic‐force microscope tips

http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

The underlying mechanisms of image distortions in atomic force microscopy (AFM) with CO-terminated tips are identified and studied in detail. AFM measurements of a partially fluorinated hydrocarbon molecule recorded with a CO-terminated tip are compared with state-of-the-art ab initio calculations. The hydrogenated and fluorinated carbon rings in the molecule appear different in size, which primarily originates from the different extents of their π-electrons. Further, tilting of the CO at the tip, induced by van der Waals forces, enlarges the apparent size of parts of the molecule by up to 50%. Moreover, the CO tilting in response to local Pauli repulsion causes a significant sharpening of the molecule bonds in AFM imaging.

Image distortions of a partially fluorinated hydrocarbon molecule in atomic force microscopy with carbon monoxide terminated tips.

The design of a monomolecular barrow 1.6 nm×1.5 nm in dimension made of a central board, two rear legs and two front wheels, is discussed. This barrow is guided and driven by the tip apex of an STM which manipulates it from the rear legs. The central board has been chosen in such a way that the rotation of the front wheels can be deduced from the surface tunnelling current intensity measured during a sequence of manipulations of the barrow. Our calculations show that in UHV and without friction, the front wheels of the barrow that we designed will not rotate. This led us to design a new barrow including two ratchet molecular groups to compensate for the absence of friction.

The design of a nanoscale molecular barrow

TBPP molecules on copper surfaces: a low temperature scanning tunneling microscope investigation

Scanning-tunneling-microscopy images of the Si(111) \ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3 -Sb surface show a trigonal lattice of protrusions, with a characteristic dependence on bias voltage. When probing filled surface states, the protrusions consist of three topographic maxima, while probing empty surface states gives a single maximum. These observations are interpreted in terms of an Sb-trimer model, the structure of which is obtained through first-principles calculations. Charge-density contours show that the three maxima seen when probing filled states can be directly related to the positions of the Sb-trimer atoms.

Evidence for trimer reconstruction of Si(111) √3 × √3 -Sb: Scanning tunneling microscopy and first-principles theory

We present spatially resolved vibronic spectroscopy of individual pentacene molecules in a double-barrier tunneling junction. It is observed that even for this effective single-level system the energy dissipation associated with electron attachment varies spatially by more than a factor of 2. This is in contrast to the usual treatment of electron-vibron coupling in the Franck-Condon picture. Our experiments unambiguously prove that the local symmetry of initial and final wave function determines the dissipation in electron transport.

/pdf/symmetry-dependence-of-vibration-assisted-tunneling-117bezmnkf.pdf

Gerhard Meyer

Papers

Image distortions of a partially fluorinated hydrocarbon molecule in atomic force microscopy with carbon monoxide terminated tips.

The design of a nanoscale molecular barrow

TBPP molecules on copper surfaces: a low temperature scanning tunneling microscope investigation

Evidence for trimer reconstruction of Si(111) √3 × √3 -Sb: Scanning tunneling microscopy and first-principles theory

Symmetry dependence of vibration-assisted tunneling.