The development of powerful structure prediction methods and codes, such as our USPEX code [1-3] enables prediction of materials with superior or unusual properties. I will discuss several thrusts of our recent work and related fundamental questions:
A. Search for superhard and ultrahard materials. Discovery of new ultrahard phases (e.g. MnB3 [4]) in apparently well-studied systems at normal conditions. Phase diagram of the elusive C-N system [5]. Can a material harder than diamond exist? [6,7].
B. Low-dimensional systems. New techniques have been developed to deal with surfaces, 2D-crystals, polymers. Recently, we made discovered two new high-permittivity polymers [8], and predicted a 2D boron crystal, much more stable than previous proposals and having massless Dirac fermions [9].
C. Search for exotic chemistry, which produces unusual materials.
Recently, we predicted a new hydrogen hydrate H2O*2H2 (i.e. H6O) to be stable at pressures above 38 GPa [10]; having 18 wt.% of easily removable hydrogen, this could be an ideal energy storage material if one can find a way of stabilizing it at normal conditions.
More intriguingly, we have discovered a class of “impossible” chemical compounds – such as Na3Cl, Na2Cl, Na3Cl2, NaCl3, NaCl7 [11] – to become stable under pressure. More recently, we predicted some of such compounds, e.g. KCl3, to be stable at normal conditions [12]. KCl3 can find industrial use as a chlorine storage material.
I will also discuss our recent discovery of stable compounds of helium at experimentally reachable pressures - Na2He and Na2HeO [13].
References
[1] Oganov A.R., Glass C.W., J.Chem.Phys. 124, 244704 (2006).
[2] Oganov A.R., Lyakhov A.O., Valle M., Acc. Chem. Res. 44, 227-237 (2011).
[3] Lyakhov A.O., Oganov A.R., Stokes H.T., Zhu Q., Comp. Phys. Comm. 184, 1172-1182 (2013).
[4] Niu H.Y., et al., Phys. Chem. Chem. Phys., in press. (2014).
[5] Dong H.F., Oganov A.R., Zhu Q., Qian G.R. In prep. (2014).
[6] Lyakhov A.O., Oganov A.R., Phys. Rev. B84, 092103 (2011).
[7] Oganov A.R., et al.,In: Comprehensive Hard Materials Review (v.3), Elsevier, 59-79 (2014).
[8] Sharma V., et al., Nature Communications, in press. (2014).
[9] Zhou X.-F., Oganov A.R., Qian G.R., Zhu Q., Phys. Rev. Lett. 109, 245503 (2012).
[10] Qian G.R., Lyakhov A.O., Zhu Q., Oganov A.R., Dong X. Scientific Reports, in press.
[11] Zhang W.W., Oganov A.R., Goncharov A.F., et al., Science 342, 1502-1505 (2013).
[12] Zhang W.W., et al. Submitted. (2014).
[13] Dong X., et al..Submitted (2014).