Rubidium Polyhydrides Under Pressure: Emergence of the Linear H3- Anion

The structures of compressed rubidium polyhydrides, RbHn with n>1, and their evolution under pressure are studied using density functional theory calculations. These phases, which start to stabilize at only P=2 GPa, consist of Rb+ cations and one or more of the following species: H- anions, H2 molecules, and H3- units. The latter motif, the simplest example of a three-center four-electron bond, is found in the most stable structures, RbH5 and RbH3. Pressure induces the symmetrization of H3-. The thermodynamically most stable polyhydrides metallize above 200 GPa. At the highest pressures studied, our evolutionary searches find an RbH6 phase which contains polymeric (H3-)$_\infty$ chains that show signs of one-dimensional liquid-like behavior

Superconducting High Pressure Phases Composed of Hydrogen and Iodine

Evolutionary structure searches predict three new phases of iodine polyhydrides stable under pressure. Insulating P1-H5I, consisting of zigzag chains of HI (delta+)and H2(delta-) molecules, is stable between 30-90 GPa. Cmcm-H2I and P6/mmm-H4I are found on the 100, 150 and 200 GPa convex hulls. These two phases are good metals, even at 1 atm, because they consist of monoatomic lattices of iodine. At 100 GPa the Tc of H2I and H4I are estimated to be 7.8 and 17.5 K, respectively. The increase in Tc relative to elemental iodine results from a larger omega-log from the light mass of hydrogen, and an enhanced lambda from modes containing H/I and H/H vibrations.Comment: 5 pages, 4 figure

Climate readiness indicators for agriculture

Countries vary in their institutional technical and financial abilities to prepare for climate change in agriculture and to balance food security, adaptation, and mitigation goals.Indicators for climate readiness provide guidance to countries and enable monitoring progress. Readiness assessments can enable donors, investors and national decision-makers to identify where investments are needed or likely to be successful. Examples of climate readiness indicators are provided for five work areas: 1. governance and stakeholder engagement, 2. knowledge and information services, 3. climate-smart agricultural strategy and implementation frameworks, 4. national and subnational capabilities and 5. national information and accounting systems