Prof. Yanming Ma [Jilin University, China]

Title: Computational design of novel compounds and room-temperature superconductors at high-pressure conditions | 新的化合物和室温超导体在高压条件下的计算设计

Time: 10:00 - 11:00 AM, Wednesday, December 28, 2016

Place: Conference room 410, HPSTAR (Shanghai)

Host: Dr. Bin Chen

Abstract

Pressure, which is a fundamental thermodynamic control on materials’ properties, reduces inter-atomic distances and profoundly modifies electronic orbitals and bonding patterns. High pressure has been a versatile tool for creating exotic materials that are not accessible at ambient conditions.

Recently, crystal structure prediction has played a leading role in major high-pressure discoveries [1]. Among various structure prediction methods, CALYPSO [2] is developed on top of swarm-intelligence algorithms by taking the advantage of swarm structures smart learning (see more at http://www.calypso.cn).

Application of CALYPSO method into exploration of high-pressure structures has generated a number of exciting discoveries. Recent examples will point to the chemical reactions of N2-Xe, Hg-F, and Au-Li at high pressures with the formation of unusual compounds N6Xe, HgF4 and AuLix (x>3) [3-5], respectively. Au loses its chemical identity, and acts as a 6p element by achieving high negative oxidation state (≥-2) in AuLi4 and AuLi5 [4], and Hg becomes a real transition metal by opening up its 5d electronic shell [5].

Emphasis will also be placed on our prediction of high-Tc superconductivity of compressed H2S [6], which led to the experimental observation of record high 200 K superconductivity. Research works towards to the design of room-T superconductors in compressed H-rich materials will be presented, including design of high Tc (>100 K) superconductor of TeH4, the highest H-content superconductor in chalcogen hydrides [7], and the exciting design of room-T superconductors in metal hydrides.

References

[1] Y. Wang and Y. Ma, J. Chem. Phys. 140, 040901 (2014).

[2] Y. Wang, J. Lv, L.Zhu, and Y. Ma, Phys. Rev. B 82, 094116 (2010); Comput. Phys. Commun. 183, 2063 (2012).

[3] Peng, et al, Phys. Rev. B. 92, 094104 (2015)

[4] G. Yang, et al., J. Am. Chem. Soc. 138, 4046 (2016)

[5] Botana et al., Angew. Chem. Int. Edit. 54, 9280 (2015)

[6] Y. Li, et al, J. Chem. Phys. 140, 174712 (2014).

[7] X. Zhong, et al, Phys. Rev. Lett. 116, 057002 (2016)

Biography of the Speaker:

Dr. Yanming Ma (http://mym.calypso.cn) received his Ph.D degree from Jilin University, China, in 2001. He then spent several years in National research council of Canada, ETH of Zurich, RIKEN of Japan, Hongkong University for long-term postdoctoral or short-term collaboration researches. He is currently a full Professor in Jilin University. His research interests mainly focus on development of simulation methods on structure prediction and exploration of new physics and chemistry of condensed matters under high pressure. He and his team have developed an efficient CALYPSO method and its same-name code for structure prediction based on swarm intelligence algorithm. More than 1600 users in 55 different countries have conducted their researches using the CALYPSO method. The resultant research papers are now beyond 330.