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In the past few years, significant interest is shown on the metastable materials across
various scientific and engineering disciplines. Among these materials, atomic and
molecular metastable solids are two vital topics where integrative research covering
several fields produced exciting results.
Physical or chemical phenomena in atomic and molecular solids having microstructural
origin show implications in physics, materials science, biology, and industry1 where
understanding and modification of different properties (such as, physical, chemical,
electrical, optical, mechanical, magnetic etc.) are pursued actively. Scientifically, atomic
or molecular metastable solids are produced predominantly from crystalline materials
either by changing chemical microstructure or by creating lattice defects or a combination
of both.2 However, limited availability of proper instruments slows down the systematic
study on these types of materials.
Among such solids, the most common molecular solid is water ice. It is believed that
crystalline ice (glaciers) shaped the present landscape of earth. Basic reactions that lead
to destruction of ozone layer take place on ice surfaces. Amorphous ice is also exciting as
phenomenon like adsorption; diffusion, wetting and solubility remarkably deviate with
respect to crystalline phase. Restructuring of ice surfaces leads to chemical reactivity
changes in an unprecedented scale.3,4 Despite several challenges, upon building advanced
instrument5, such type of events were identified.
Progress in modern instrumentation also produced unusual type of amorphous solid
known as nanoglass.6,7 In the case of common metastable atomic solids (or amorphous
alloy), chemical compositions define their properties, which is difficult to alter. In
contrary to crystalline solids, introduction of microstructural defects in amorphous solids
while maintaining identical chemical composition is not possible. This problem was
solved upon preparing ‘nanoglass’. The ability to tune mechanical, magnetic, electrical
and catalytic properties in a nanoglass (because of the free volume) added flexibility in
research of this new class of materials. Instrumental developments, which aided the
synthesis of nanoglasses, ability to perform microstructure analysis (experimental and
computational) with atomistic details enriched the area for further development.
References:
1. Bag, S.; Bhuin, R. G.; Natarajan, G.; Pradeep, T., Probing molecular solids with
low-energy ions. Annu. Rev. Anal. Chem. 2013, 6, 97 - 118.
2. Danilov, D; Hahn, H; Gleiter, H; Wenzel, W., Mechanism of nanoglass
ultrastability. ACS Nano 2016, 10, 3241 – 3247.
3. Bag, S; McCoustra, M. R. S.; Pradeep, T. Formation of H2
+ by ultra-low energy |