From first principles calculations, we show that (InN)32 nanoparticles favor rock salt structure compared with wurtzite structure in bulk. A phase transition from wurtzite to rock salt structure is known to occur in bulk InN at 12.1 GPa and higher values of pressure for AlN and GaN. However, at the nanoscale we show that this structural transition takes place in (InN)32 without applying pressure. The charge asymmetry value g and cationanion size ratio in InN describe very well this behavior. Similar studies on nanoparticles of AlN and GaN as well as a few other binary compounds such as MgS, AgI, ZnO, and CdSe, however, do not show such a transition. Our results suggest (InN)32 to be a unique candidate as further calculations on a few larger size (InN)n nanoparticles show that a filled cage (two shells) (InN)12at(InN)48 structure of (InN)60 has higher binding energy compared with a rock salt structure of (InN) 64 leading to the conclusion that other 3D structures are likely to become favorable over rock salt structure for larger sizes. © 2013 American Institute of Physics.

Vijay Kumar

Center for Informatics

Kaur P.

Sekhon S.S.

Fulltext

<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

Prediction of rock salt structure of (InN)32 nanoparticles from first principles calculations.

Journal of Chemical Physics

The discovery of carbon fullerene cages and their solids opened a new avenue to build materials from stable cage clusters as "artificial atoms"or "superatoms"instead of atoms. However, cage clusters of other elements are generally not stable. In 2001, ab initio calculations showed that endohedral doping of Zr and Ti atoms leads to highly stable Zr@Si16 fullerene and Ti@Si16 Frank-Kasper polyhedral clusters with large HOMO-LUMO gaps. In 2002, Zr@Ge16 was shown to form a Frank-Kasper polyhedron, suggesting the possibility of designing novel clusters by tuning endohedral and cage atoms. These results were subsequently confirmed from experiments. In the past nearly two decades, many experimental and theoretical studies have been carried out on different clusters, and many very stable cage clusters with possibly high abundance have been found by endohedral doping. Indeed in 2017, Ta@Si16 and Ti@Si16 cage clusters have been synthesized in bulk quantity of about 100 mg using a dry-chemistry method, giving rise to a new hope of developing cluster-based materials in macroscopic quantity besides the well-known C60 fullerene solid. Also, wet-chemistry methods have been used to synthesize endohedrally doped clusters as well as ligated clusters and their solids, which auger well for the development of novel nanostructured materials using atomically precise clusters with unique properties. In this comprehensive review, we present results of many such developments in this fast-growing field including (i) endohedrally doped Al, Ga, and In clusters, (ii) small endohedral carbon fullerene cages with ≤ 28 carbon atoms, (iii) metal doped boron cages, (iv) endohedrally doped cages of group 14 elements (Si, Ge, Sn, and Pb), (v) coinage metal (Cu, Ag, Au) cages doped with a transition metal atom as well as their ligated clusters and crystals, (vi) endohedrally doped cages of compound semiconductors, and (vii) multilayer Matryoshka cages and core-shell structures. In a large number of cases, we have performed ab initio calculations to present updated results of the most stable atomic structures and fundamental electronic properties of the endohedrally doped cage clusters. We discuss electronic, magnetic, optical, and catalytic properties in order to shed light on their potential applications. The stability of the doped cage clusters has been correlated to the concept of filling the electronic shells for superatoms such as within a spherical potential model and also using various electron counting rules including Wade-Mingos rules, systems with 18 and 32 electrons, and the spherical aromaticity rule. We also discuss cluster-cluster interaction in cluster dimers and assemblies of some of the promising doped cage clusters in different dimensions. Finally, we give a perspective of this field with a bright future. © 2020 American Chemical Society.

Chemical Reviews

Endohedrally Doped Cage Clusters

Results of ab initio pseudopotential calculations are presented concerning the atomic structure and magnetic properties of GaN doped with selected rare earth atoms. Effects of codoping these materials with Si are also discussed. It has been found that the doping of a Eu atom on a Ga site in bulk GaN creates significant local deformation and it costs 1.84eV. However, the addition of a Si atom makes Eu doping in bulk GaN energetically favorable as strain from an oversized Eu atom and an undersized Si atom is compensated. Therefore codoping of Si facilitates doping of rare earths in GaN. The excess charge due to codoping of Si tends to cause Eu to be in a 2+ state and the magnetic moment on Eu ion is enhanced to 7μB. Further studies have shown that Eu atoms tend to cluster with interatomic separation of about 5Å and there is ferromagnetic coupling. For rare earth atoms in nanoparticles, ab initio calculations have been performed on (GaN)n (n=12, 16, 22, and 32) nanoclusters with Eu, Gd, and Nd atoms substituting on Ga sites. These studies have yielded preferred atomic structures and magnetic behavior. Cage structures of these GaN nanoclusters were found to be lower in energy as compared to bulk fragments. Specific results show that Eu-doping in GaN nanoparticles is favorable compared with bulk GaN since a large fraction of atoms in a nanocluster lie on the surface where strain can be lower. Codoping of Si further facilitates Eu doping as in the case of bulk GaN. © 2016 Elsevier Ltd. All rights reserved.

Rare Earth and Transition Metal Doping of Semiconductor Materials: Synthesis, Magnetic Properties and Room Temperature Spintronics

Energetics, atomic structure, and magnetics of rare earth-doped GaN bulk and nanoparticles

Physical Review B

Empty cage to three-dimensional structural transition in nanoparticles of III-V compound semiconductors: The finding of magic (AlP)13and (GaP)32

The Journal of Chemical Physics

(PbS)32: A baby crystal

Computational and Theoretical Chemistry

Mechanism of the phase transition in GaN under pressure up to 100GPa

Computational Materials Science

First-principles calculations of pressure-induced phase transformation in AlN and GaN

Journal of Alloys and Compounds

Pressure-induced phase transition in AlN: An ab initio molecular dynamics study

Prediction of rock salt structure of (InN)32 nanoparticles from first principles calculations