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

Machine learning shows how hydrogen becomes a metal inside giant planets

10 September 2020

By combining machine learning and quantum mechanics, researchers have carried out simulations to discover how hydrogen becomes a metal under extreme pressures.

MSM-AIMR Joint Online Workshop 2020

8 September 2020

In the week of 24-28 August 2020, the Department of Materials Science and Metallurgy held a Joint Online Workshop with Tohoku University in Japan.

Hierarchically Structured Allotropes of Phosphorus from Data-Driven Exploration

22 June 2020

Researchers discover new elemental phosphorus structures by using 'fragments' of phosphorus as building blocks.

New academic license for CASTEP

6 March 2020

The CASTEP developers announce a new cost-free worldwide source code license to CASTEP and NMR CASTEP for academic use.

Dr Chuck Witt joins the MTG

6 March 2020

The Materials Theory Group welcomes its newest research associate, Dr Chuck Witt.

Welcome to Dr Bartomeu Monserrat

10 January 2020

The Materials Theory Group welcomes new faculty member and new group member Bartomeu Monserrat.

CASTEP: From research code to software product with Professor Chris Pickard

9 January 2020

On 22 January 2020, Chris Pickard will give a talk followed by a Q&A session on commercialising software.