skip to content
 

Materials Modelling Seminar

Professor Maosheng Miao, Department of Chemistry and Biochemistry, California State University Northridge, CA 91330, USA

Tuesday 20th Mar., 14:00

Goldsmiths 1 (0_017), Department of Materials Science & Metallurgy

Title: Simulate to discover: from new chemistry under high pressure to novel two-dimensional materials

Abstract:

The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry, rooted in the atomic shell structure. Within compounds, Group I elements, for example, invariably assume the +1 oxidation state, and their chemical properties differ completely from those of the p-block elements. These general rules govern our understanding of chemical structures and reactions. Using first principles calculations, we demonstrate that under high pressure, the above doctrines can be broken. We show that both the inner shell electrons and the outer shell empty orbitals of Cs and other elements can involve in chemical reactions. Furthermore, we show that the quantized orbitals of the enclosed interstitial space may play the same role as atomic orbitals, an unprecedented view that led us to a unified theory for the recently observed high-pressure electride phenomenon. In the last example for high-pressure chemistry, we demonstrate that He can form stable compounds with ionic crystals. The driving force for these reactions is not the local chemical bonds but rather the alternation of the long-range Coulomb interactions among ions while incorporating He atoms in the lattice.

Furthermore, we show the development of an efficient method that can automatically explore the surface structures by virtue of structure swarm intelligence. While applying the method on the "simple" diamond (100) surface, we discovered a hitherto unexpected surface reconstruction featuring self-assembly of carbon nanotubes (CNTs) arrays. The intriguing covalent bonding between the neighboring tubes creates a unique feature of carrier kinetics ---one dimensionality of hole states whereas two dimensionality of electron states, which may lead to novel design of superior electronics. Using very different approach, we propose and demonstrate a large family of two-dimensional semiconductors (2DSC), all adopting the same structure and consisting of only main group elements. We demonstrate the attainability of these materials, and show that they cover a large range of lattice constants, band gaps and band edge states, therefore are good candidate materials for heterojunctions. The new 2DSCs may pave a way toward fabrication of 2DSC devices at the same thriving level as 3D semiconductors.

talks.cam: http://talks.cam.ac.uk/talk/index/101599

Latest news

Visualising potential energy surfaces using dimensionality reduction

25 November 2021

Computational structure prediction has emerged as a highly successful approach to the discovery of new materials. Candidate structures are created by constructing the most stable configurations that can be adopted by a given...

The elements of life under pressure

1 July 2021

First-principles structure prediction sheds light on high-pressure compounds formed from carbon, hydrogen, nitrogen and oxygen.

AIRSS for battery cathode materials

15 June 2021

A team of researchers at Cambridge and University College London have developed a computational framework for battery cathode exploration based on ab initio random structure searching.

Anatase-like Grain Boundary Structure in Rutile Titanium Dioxide

30 April 2021

A collaboration between researchers at Cambridge and AIMR has shed light on grain boundary structures in titania.

Physics World Breakthrough of the Year finalists for 2020

17 December 2020

A paper coauthored by Chris Pickard and Bartomeu Monserrat has been selected as a Top 10 finalist in Physics World's breakthroughs of the year for 2020.

An upper limit for the speed of sound

17 November 2020

A collaboration involving Bartomeu Monserrat and Chris Pickard was featured on both the University website and the Department website .

New fellowships for Chuck

17 November 2020

Congratulations to Chuck Witt, who began recently as a Schmidt Science Fellow and as a Junior Research Fellow at Christ's College, Cambridge! The Schmidt award is intended to catalyze new research directions and...