Computation of the stabilities and crystal structures of known and new phosphorus allotropes made of nanotubes
What holds white, black, and red phosphorus together—and prevents it from falling apart, for example into much-sought-after atomically thin networks and nanowires? This is what German scientists now found out using numerical modeling. As they explain in the journal Angewandte Chemie, Van der Waals forces, weak interactions between covalently bonded phosphorus units, play the key role.
Phosphorus occurs in several different forms—more than those described in classic textbooks. They each consist of different molecular building blocks aggregated into a solid. Reactive, white phosphorus is used in matchsticks, among other things, and exists in three different crystal structures.
These all consist of individual tetrahedra made of phosphorus atoms, but the tetrahedra are arranged differently within the different crystal structures. Under pressure—or by means of a new method developed by Tom Nilges (TU Munich) and Peer Schmidt (BTU Cottbus-Senftenberg)—white phosphorus can be converted to inert black phosphorus, the most stable form at room temperature.
This form and another high-pressure allotrope both consist of corrugated layers of phosphorus atoms. The isolation of individual layers to make “phosphorene” (analogous to graphene) is the object of current research. When white phosphorus is heated, it is converted to various forms of red phosphorus. Until recently, only the structure of one of these, violet Hittorf’s phosphorus, was known. It consists of pentagonal nanotubes of covalently bonded phosphorus atoms.
In recent years, Arno Pfitzner (University of Regensburg), Michael Ruck (TU Dresden), and other researchers have produced other allotropes containing single and paired phosphorus nanotubes that occur as fibrous red crystals or red-brown variants. The structures of the nanotube modifications and the stabilities of the new forms relative to the known ones remained unclear.
Richard Weihrich, Arno Pfitzner, and their co-workers at the University of Regensburg, RWTH Aachen, BTU Cottbus-Senftenberg, and TU Munich have now successfully used density functional theory (DFT) to establish the order of stability for the entire series of crystalline phosphorus allotropes and to determine the structures of the new single-rod modifications. Although conventional DFT calculations were too imprecise, the researchers were able to obtain excellent agreement with experimental results and precise predictions by using a special correction term.
This term takes into consideration the Van der Waals forces, weak interactions between the molecules, layers, and tubes of the different forms. These interactions play a significant role for phosphorus. “Despite significant differences, all phosphorus allotropes consist of covalent substructures that are held together by Van der Waals interactions,” explains Weihrich. “We have now been able to comprehensively compute the stabilities of even those allotropes that are energetically very similar.
We have also been able to correctly predict structures on the basis of the van der Waals interactions. It was thus also possible to integrate the recently discovered tubular modifications and to predict the structure of the previously unknown crystalline structures of phosphorus nanotubes.” These weak interactions are highly relevant to new research into single- and multiple-layer “phosphorenes” as well as the possible separation of individual phosphorus nanotubes.
Dr. Richard Weihrich leads a research group at the Institute of Inorganic chemistry, University of Regensburg, Germany. Over the last 12 years, he has worked in fields of solid-state chemistry in Regensburg, Bordeaux, Paris, Dresden, and Ulm. With combined experimental and computer-assisted methods he explores novel materials with outstanding structure–property relations including spintronics, superconductors, and energy-based materials. His research on phosphorous related materials is founded by the DFG (Deutsche Forschungsgemeinschaft).
Author: Richard Weihrich, Universität Regensburg (Germany), http://www.uni-regensburg.de/chemie-pharmazie/anorganische-chemie-weihrich/
Title: The Extended Stability Range of Phosphorus Allotropes
Angewandte Chemie International Edition Permalink to the original article: http://dx.doi.org/10.1002/anie.201404147 – Please use in your news piece to make sure altmetric.com picks it up and a link to your piece is shown on the journal's website.
Richard Weihrich | Angewandte Chemie
First time-lapse footage of cell activity during limb regeneration
25.10.2016 | eLife
Phenotype at the push of a button
25.10.2016 | Institut für Pflanzenbiochemie
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
26.10.2016 | Physics and Astronomy
26.10.2016 | Earth Sciences
25.10.2016 | Earth Sciences