Researchers have thoroughly analyzed the mechanisms underlying the flexibility of metal-organic frameworks (MOF) crystals and attributed this flexibility to extensive structural rearrangements associated with soft and hard vibrations within the crystal that strongly couple strain fields, opening the door to novel materials with diverse applications in various analytical industries.
Metal-organic frameworks (MOFs) are a large class of crystalline materials that have remarkable abilities to absorb and store gases such as carbon dioxide as well as act as filters for the purification of crude oil. MOFs derive this ability from the presence of nanopores, which increase their surface areas, and which in turn make them efficient in absorbing and storing gases. However, limited stability and mechanical fragility have hindered their widespread applications.
Addressing this problem, Professor Umesh V. Waghmare and his team from the Theoretical Sciences Unit at Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, an autonomous institute under the Department of Science and Technology (DST), Government of India, have recently proposed a new quantitative measure of mechanical flexibility for a crystal that can be used to screen materials databases to identify next-generation flexible materials.
His paper, “Quantifying the intrinsic mechanical flexibility of crystalline materials”, presents unprecedented insights into the origin of mechanical flexibility and was published in the journal Physical Review B. Professor Waghmare's research focuses particularly on MOFs, which are known for their beautiful crystalline structure and great flexibility.
Historically, elasticity in any crystal has been evaluated in terms of a parameter called the elastic modulus, which is a measure of the material's resistance to strain-induced deformation. In contrast, this study proposes a unique theoretical measure based on the fractional release of elastic strain or strain energy through internal structural rearrangements under symmetry constraints. This new metric can be easily calculated using standard techniques of simulation and can calibrate the elasticity of a crystal on a scale from zero to one, with zero indicating the least elasticity while one indicating the maximum elasticity. Additionally, this discovery provides a unique and quantitative insight into the elasticity of crystals, a dimension that was hitherto unknown.
Although this proposed measurement of elasticity is still theoretical, experimentalists will find it very useful. The potential applications of this research go beyond the realm of physics, opening the door to new materials with diverse applications in a variety of industries.
Paving the way to a new paradigm in materials research, this research study exemplifies the importance of interdisciplinary collaboration and theoretical advances in shaping the future of materials science.
Publication link: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.108.214106