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Theoretical Simulation of Nanoclustersm (2) Theoretical simulation of Nanoclustersm (2) Xiaohu Yu Moscow Institute of Physics and Technology Contents • Introduction of clusters and theoretical methods • The stability and geometric structure of different clusters • Design the different superatoms • Conclusion Introduction • Clusters: a bridge across disciplines • Clusters: an embryomnic form of matters • Clusters: made by laboratory, often metastable, composition can change • Molecule: made by nature, belong clusters • Superatom: unique stability and properties of clusters, building blocks Theoretical Methods • Quantum chemical approach • Density functional theory • Genetic program • Basin hopping method • Evolutionary program Superatom and magic number • 1992, superatom • Jellium model • Octet rule • 18 electron rule • Wade-Mingos rule • Superhalogen • Superalkali Shiv Khanna Puru Jena J. Phys.Chem. Lett.4(2013) 1432 Weakly interaction cluster 1981,Echt and coworkers a mass spectrum of xenon, N = 1+∑(10p2+2) Noble gas atom exhibit stability at 13, 55, 147…. Atomic shell closure 8-e rule 18-e rule • Transition metal carbonyl • 18 electron rule Jellium model • 1984, Knight and coworkers Alkali metals • 1984 Knight and coworkers • Magic number 2,8,20,40,58,and 92 • 1s2, 1p6,1d10,2s2,1f14,2p6, 1g18…. • Na cation clusters should be 3, 9, 21, 41, 59,93… • Odd-even alternation (Jahn-Teller effect) • The similarity between magic numbers in nuclei and atomic clusters • Bridge nuclear and condensed-matter physics • Electronic shell closure Na J. Chem. Phys. 123(2005) 164310. Alkali-earth metal clusters • Shell closure effects: 2, 8, 20, 34, 40 Be J. Chem. Phys. 123(2005) 074329. Al cluster superatoms Al13 cluster behave like a halogen atom Al14 cluster exhibits properties analogous to alkaline earth atom Bergeron et al. Science 307(2005) 231 Multiple valence superatoms • Al13 cluster behave like a halogen atom • Al14 cluster exhibits properties analogous to alkaline earth atom - • Al7 exhibits multiple valence Reveles et al. Natl. Acad. Sci. USA. 103(2006) 18405 Coinage metal clusters • Cu, Ag, Au monovalent like alkali metal • Stability like alkali metal • The geometric structure is different with alkali • Au unique Au J. Chem. Phys. 132 (2010) 054305 Transition-metal clusters • Unfilled d-orbital • Different structure with simple metals Ni J. Phys. Chem. A, 1997, 101 (6), pp 1072 Semiconductor clusters • Odd-even alternation at n<8 • Odd cluster is more stable than even cluster • Ring or cage is favored at more C atoms • fullerene J. Chem. Phys. 87(1987); 2191 Semiconductor clusters Nature 1998;392:582 Bialloy clusters Al12Au20 J. Chem. Phys. 131(2009) 204501 BxHy(borane) • Wade-Mingos rule: stability of boranes requires (n+1) pairs of electrons, where n is the number of vortices of a boron polyhedron. • AlxHy • Polyhedral skeletal electron pair theory (PSEPT) Ionically bonded cluster • (MgO)x, (CaO)x, (NaCl)x and so on • X=4, 13,22,37…. • One part of bulk J. Chem. Phys. 106(1997) , 2323 Superhalogen • EA (electron affinity) of Cl, 3.62 eV • Bartlett and Lohmann PtF6 • 1981, Gutsev and Boldyrev showed a central metal atom decorating with halogen ligands (coined superhalogen) Gutsev et al. Chem. Phys. 56(1981) 277 Gutsev et al. Chem. Phys. Lett. 92(1982) 262 Mn-based magnetic superhalogens - • MnnCl2n+1 stabilize by superhalogen • Not by electronic shell closure or atomic shell closure • Mn2+ and high-spin d5 configuration, extra electron localizes 3Cl, high EA (5 eV>3.62 eV Cl) Wu et al. Angew.Chem.Int.Ed.2001,50, 2568-2572 Hyperhalogen • The peripheral halogen atoms replace by superhalogen molieties. Willis et al. Angew. Chem. Int. Ed. 2010, 49,8966-8970 Superalkali • Ionization potentials (IPs) of alkali metal (5.4-3.9 eV) • 1981, Gutsev and Boldyrev • Superalkali: ionization potentials (IPs) lower than 3.9 eV(cesium) • Formulation of superalkali MLk+n Gutsev et al. Chem. Phys. 56(1981) 277 Gutsev et al. Chem. Phys. Lett. 92(1982) 262 Superalkali • Lower ionization potentials (IPs) than alkali metal atoms (5.4-3.9 eV). Sun et al. Inorg. Chem. 53 (2014) 6170 Design Superalkali cations • Lower the electron affinity by halogenation Hou et al. J. Am.Chem.Soc. 136 (2014) 2921 Aromatic Superatoms • Aromatic superalkali cations by replacing the atomic M cores with aromatic anions J. Phys.Chem. C 117(2013) 24618 Designer magnetic superatoms • Doping simple metal clusters with magnetic atoms • VNa8 is magnetic superatom with a filled d-subshell and a magnetic moment (5 μB) Zhang et al. J. Am. Chem. Soc. 135(2013) 4856 Designer magnetic superatoms • Magnetic superatoms can be designed by combinations of localized and delocalized electrons in the valence space of a cluster Reveles et al. Nat. Chem. 1(2009) 310 Hunt’s rule in superatom 2 2 2 • The D states are split into a group of (Dxy, Dx -y , Dxz, and Dyz) and a Dz state • Fe has 4s2 and 3d6, Mg has 3S2 Medel et al. Natl. Acad. Sci. USA. 108(2011)10062 S-P coupling induced unusual Open-shell metal clusters - - - • Al5Mg2 and Al11Mg3 have 20 and 40 e (electronic shell closure) - • Al2Mg clusters originate from S-P molecular orbital coupling Cheng et al. J. Am. Chem. Soc. 136(2014) 4821 Met-Cars • Met-Cars (Metallocarbohedrynes) • Ti8C12 (Ti, Zr, Hf, V, and Nb, Cr, Mo, Fe) Science 255(1992) 1411 Conclusion • Clusters: a bridge across disciplines • The stability of nanocluster: magic number and superatoms • Different kinds of clusters • Design the superatoms .
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