Computer aided design of nanomaterials

Novel structures of clusters of semiconductors and metals obtained from
ab initio calculations
Vijay Kumar
Dr. Vijay Kumar Foundation, 1969 Sector 4, Gurgaon 122001
Properties of matter at the nanoscale are often vastly different from bulk and depend on size
and shape in addition to the well known factors of composition and thermodynamic variables.
Therefore exciting new opportunities have emerged to design materials with fine tuned
properties and new applications are becoming possible using matter at the nanoscale. Great
efforts are being made to explore new materials for miniature devices, novel catalysts for
industrial applications, fuel cells for hydrogen economy, new processes for developing
materials as well as to understand biological systems whose length scale overlaps with that of
nanomaterials. Nanoparticles, nanowires, nanotubes, and nanobelts are some of the forms that
have attracted great attention in recent years. As large fraction of atoms in these systems lie on
the surface, there is often a reconstruction that generally leads to new structure of nanoparticles
particularly in the range of size of ~ 1 nm. Computer simulations are playing a key role in
understanding the structure-property relation of such systems as well as in designing new
nanomaterials. In this talk I will discuss a few selected examples where ab initio calculations
have helped (1) to resolve long standing experimental data on nanomaterials such as magnetic
clusters of non-magnetic bulk Rh [1] which have been found to grow in simple cubic structure
and semiconductor nanoparticles of CdSe [2] for which Cd34Se34 clusters have been found to
be magic, and (2) to predict novel forms of silicon - the silicon fullerenes [3] and nanotubes [4]
with metal encapsulation that have later received experimental support [5]. More recently we
have obtained [6] novel growth behavior of Pt clusters with diameter up to 3 nm. Some recent
results on silicon nanowires [7] and MoS nanowires [8] will be also discussed.
[1] Y.-C. Bae, V. Kumar, H. Osanai, and Y. Kawazoe, PRB72, 125427 (2005).
[2] A. Kasuya et al., Nature Materials 3, 99 (2004) and to be published.
[3] V. Kumar and Y. Kawazoe, PRL 87, 045503 (2001); ibid. 90, 055502 (2003); V. Kumar,
Comput. Mater. Sci. 36, 1 (2006); A.K. Singh et al., PRB 71, 115429 (2005); V. Kumar in
“Nanosilicon”, Elsevier (2008).
[4] A. K. Singh et al., Nano Lett. 2, 1243 (2002); PRL 91, 146802 (2003).
[5] K. Koyasu et al., JACS 127, 4998 (2005); Saranin et al., Nano Lett. 4, 1469 (2004).
[6] V. Kumar and Y. Kawazoe, Phys. Rev. B77, 205418 (2008).
[7] A. K. Singh et al. Nano Lett. 5, 2302 (2005); ibid. Nano Lett. 6, (2006).
[8] P. Murugan, Nano Lett. 7 (2007); Appl. Phys. Lett. (in press).
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