The high-pressure behavior of CaMoO4

We report a high-pressure study of tetragonal scheelite-type CaMoO4 up to 29 GPa. In order to characterize its high-pressure behavior, we have combined Raman and optical-absorption measurements with density-functional theory calculations. We have found evidence of a pressure-induced phase transition near 15 GPa. Experiments and calculations agree in assigning the high-pressure phase to a monoclinic fergusonite-type structure. The reported results are consistent with previous powder x-ray-diffraction experiments, but are in contradiction with the conclusions obtained from earlier Raman measurements, which support the existence of more than one phase transition in the pressure range covered by our studies. The observed scheelite-fergusonite transition induces significant changes in the electronic band gap and phonon spectrum of CaMoO4. We have determined the pressure evolution of the band gap for the low- and high-pressure phases as well as the frequencies and pressure dependences of the Raman-active and infrared-active modes. In addition, based upon calculations of the phonon dispersion of the scheelite phase, carried out at a pressure higher than the transition pressure, we propose a possible mechanism for the reported phase transition. Furthermore, from the calculations we determined the pressure dependence of the unit-cell parameters and atomic positions of the different phases and their room-temperature equations of state. These results are compared with previous experiments showing a very good agreement. Finally, information on bond compressibility is reported and correlated with the macroscopic compressibility of CaMoO4. The reported results are of interest for the many technological applications of this oxide.Comment: 36 pages, 10 figures, 8 table

High pressure studies on α -cristobalite form of Al0.5Ga0.5PO4\mathrm{Al_{0.5}Ga_{0.5}PO_{4}} : hydrostatic versus non-hydrostatic conditions

High pressure angle-dispersive X-ray diffraction investigations have been carried out on α-cristobalite form of $\mathrm{Al_{0.5}Ga_{0.5}PO_{4}}$. Our investigations show that the structural stability of this phase under high pressure depends on the nature of pressure conditions in the diamond anvil cell. Under hydrostatic pressure conditions using neon as a pressure transmitting medium, ambient orthorhombic C222$_1$ phase transforms to orthorhombic Cmcm phase at 4.9 GPa. The high pressure Cmcm phase remains stable up to the highest pressure in the experiment, i.e. 19 GPa. The values of bulk modulus for C222$_1$ and Cmcm phases are 19(2) and 126(4) GPa, respectively. In contrast to this, under non-hydrostatic pressure conditions, transformation of ambient C222$_1$ phase to Cmcm phase has not observed up to 17.4 GPa. Instead, a new monoclinic phase P2$_1$ is observed which contains layers of six coordinated Al/Ga ions separated by less dense five coordinated Al/Ga ions

Pressure induced phase transitions in multiferroic BiFeO₃

Using synchrotron based angle dispersive x-ray diffraction measurements and first principles calculations we have studied the high pressure behavior of pervoskite BiFeO₃. We report two structural phase transitions under pressure viz., at ∼4.1 and ∼6.4 GPa. Our first principles calculations, combined with Rietveld refinement of the diffraction data, suggest that both the high pressure phases are orthorhombic, the first being P222₁ and the second phase belonging to the space group Pnma. These results are in contrast to the previous studies such as the observation of monoclinic phase below 10 GPa. Theoretical structural optimization in the present case indicates the utility of incorporating the chemical bonding in Rietveld refinement of complex structures

Not Available

Not AvailableGarib Kalyan Rojgar Abhiyaan (GKRA) initiative was announced by the government of India in June 2020 for a period of 125 days to create livelihood opportunities for the returned migrants in their states and to sustain rural development. GKRA was convergent effort between 12 different ministries/departments covering 25 activities over 116 districts of 6 states. As different stakeholders were involved, therefore for effective monitoring and data exchange an IT platform was created at central level (https://gkra.nic.in) where all departments exchanged data for consecutive 15 weeks. Indian Council of Agricultural Research (ICAR) organized skill development training programmes for livelihood through Krishi Vigyan Kendra (KVK). E-Governance of these training programmes and exchange of data to central GKRA portal was managed through a module developed during July-October 2020 under KVK Knowledge Network Portal (https://kvk.icar.gov.in) at ICAR-Indian Agricultural Statistics Research Institute and hosted at ICAR Data Centre, ICAR-IASRI, New Delhi. The emphasis of the training programmes was on the areas of integrated farming to support livelihood. Overall, the participants were satisfied with the quality of training programmes conducted by KVKs. KVKs also supported participants in handholding of technology and setting up their own venture. IT platforms provided efficient storing and retrieval of data, framework for exchange of information and enhanced visibility in the initiative.Not Availabl

Large Local Internal Stress in an Elastically Bent Molecular Crystal Revealed by Raman Shifts

The structural dynamics involved in the mechanical flexibility of molecular crystals are not well understood yet. Here, we report an elastically bending lipidated molecular crystal that shows systematic shifts in characteristic vibrational frequencies across the bent crystal region - revealing the nature of structural changes during bending and the local internal stress distribution. The elastic flexibility is rendered by intermolecular N-H∙∙∙O hydrogen-bonded chains along with strong yet flexible alkyl-chain hydrophobic interactions in this crystal structure. The blue shifts in the bond stretching modes (such as C=O and C-H modes) in the inner arc region and red shifts in the outer arc region of the bent crystals observed via micro-Raman mapping are counterintuitive to the bending models based on intermolecular hydrogen bonds. Correlating these shifts with the trends observed from high-pressure Raman studies on the crystal reveals the local stress difference between the inner arc and outer arc regions of the bent crystal to be ~2 GPa, more than an order of magnitude higher than the previously proposed value in elastically bending crystals. High local internal stress can have direct ramifications on the properties of molecular piezoelectric energy harvesters, actuators, semiconductors, and flexible optoelectronic materials

Not Available

Not AvailableA Mobile application, most commonly referred to as an app, is a type of application software designed to run on a mobile device, such as a smartphone or tablet computer. Mobile applications provide users with similar services to those accessed through personal computers. Mobile technology has transformed the information sharing in many ways. Information reach has moved one step further and even farmers are using mobiles or smartphone for getting desired information. Mobile phones are appreciated by farming communities as easy, fast and convenient way to communicate and get prompt solution to their problems. This device has given new direction and approach to farmers to communicate directly and share recent advances with each other. Government is taking steps and encouraging development of mobile application that will enable farmers across the country to get information.Not Availabl