Assessment of the performance of CORDEX Regional Climate Models in Simulating Eastern Africa Rainfall

This study evaluates the ability of 10 regional climate models (RCMs) from the Coordinated Regional Climate Downscaling Experiment (CORDEX) in simulating the characteristics of rainfall patterns over eastern Africa. The seasonal climatology, annual rainfall cycles, and interannual variability of RCM output have been assessed over three homogeneous subregions against a number of observational datasets. The ability of the RCMs in simulating large-scale global climate forcing signals is further assessed by compositing the El Niño–Southern Oscillation (ENSO) and Indian Ocean dipole (IOD) events. It is found that most RCMs reasonably simulate the main features of the rainfall climatology over the three subregions and also reproduce the majority of the documented regional responses to ENSO and IOD forcings. At the same time the analysis shows significant biases in individual models depending on subregion and season; however, the ensemble mean has better agreement with observation than individual models. In general, the analysis herein demonstrates that the multimodel ensemble mean simulates eastern Africa rainfall adequately and can therefore be used for the assessment of future climate projections for the region

Boron Hydrogen Compounds for Hydrogen Storage and as Solid Ionic Conductors

Metal borohydrides have been studied since the beginning of this century as potential hydrogen storage materials due to their high gravimetric hydrogen content. Many new compounds have been synthesized and characterized, however to date the main problem are the kinetics of dehydrogenation and rehydrogenation. In this review we address thermodynamical and chemical properties of boron hydrogen compounds which come into play for hydrogen storage and which must be considered in the search for efficient catalysts. More recently, closo and nido hydridoborate and related closo hydridocarborate compounds have been identified as good ionic conductors for all-solid-state lithium or sodium batteries. The properties of these fascinating and very promising compounds for battery applications are illustrated with recent literature results

Estimation of Thermodynamic Properties of Metal Hydroborates

Metal hydroborates from M(BH4)n to Mx(B12H12)y currently attract a strong interest for potential applications in the field of hydrogen storage and more recently as solid ionic conductors. While thermodynamic data for the alkali borohydrides (MBH4) are well known, experimental data for other compounds are cruelly lacking. Using a combination of theoretical (DFT) and experimental data, we calculate the lattice enthalpy for a series of borohydrides. The comparison with literature data show that these lattice enthalpies are very similar to those of the corresponding metal bromides. This similarity is at the origin of a good correlation between the formation enthalpy of bromides and borohydrides which is then used to estimate the previously unknown formation enthalpy of MII(BH4)2 (MII= divalent cation) and Ln(BH4)3 (Ln=lanthanide). The Gibbs free energy of formation of M2(B12H12) (M=alkali metal) is also estimated

Boron Hydrogen Compounds: Hydrogen Storage and Battery Applications

About 25 years ago, Bogdanovic and Schwickardi (B. Bogdanovic, M. Schwickardi: J. Alloys Compd. 1–9, 253 (1997) discovered the catalyzed release of hydrogen from NaAlH4. This discovery stimulated a vast research effort on light hydrides as hydrogen storage materials, in particular boron hydrogen compounds. Mg(BH4)2, with a hydrogen content of 14.9 wt %, has been extensively studied, and recent results shed new light on intermediate species formed during dehydrogenation. The chemistry of B3H8−, which is an important intermediate between BH4− and B12H122−, is presented in detail. The discovery of high ionic conductivity in the high-temperature phases of LiBH4 and Na2B12H12 opened a new research direction. The high chemical and electrochemical stability of closo-hydroborates has stimulated new research for their applications in batteries. Very recently, an all-solid-state 4 V Na battery prototype using a Na4(CB11H12)2(B12H12) solid electrolyte has been demonstrated. In this review, we present the current knowledge of possible reaction pathways involved in the successive hydrogen release reactions from BH4− to B12H122−, and a discussion of relevant necessary properties for high-ionic-conduction materials.</p

Low-temperature raman spectra of bis(ethylammonium)tetrachlorocadmate (EACdC) and two isotopic analogs

We have obtained polaried Raman spectra of (CH3CH2NH3)2CdCl4 (EACdC), (CD3CH2NH3)2CdCl4 [EACdC-d3(I)], and (CH3CH2ND3)2 CdCl4 [EACdC-d3(II)] between 20 and 230 cm−1 at temperatures from 4.2 to 50 K. A virational assignment is proposed on the basis of isotopic substitutions. A monoclinic crystal structure at these temperatures is postulated

Raman spectroscopic study of structural phase transitions in the layer crystals (EtNH3)2MCl4 with M=Cd and Mn

The authors have studied the Raman spectra of the crystals (EtNH3)2MCl4 (M=Cd and Mn) as functions of temperature from 5 to 300K. The external vibrations have been assigned. The space group of the Cd crystal below 114K is found to be P22/b and the phase transition P21/b-Pbca is described as a displacive first-order transition. The order-disorder transitions Pbca-Abma in (EtNH3)2MCl4 for M=Cd and M=Mn are compared. Linewidth measurements performed on the carbon-carbon stretching mode at about 870 cm-1 suggest the possibility of a second-order transition in the Mn crystal, while the first-order behaviour of the transition in the Cd crystal is confirmed

Raman investigation on structural phase transitions in (C2H5NH3)2CdCl4

We have investigated the structural phase transitions at 114 and 316 K in (C2H5NH3)2CdCl4 (= EACdC) by Roman spectroscopy. These measurements provide more information about the symmetry low-temperature monoclinic phase, new results on the phase transition at 114 K and additional data on the order-disorder transition at 216 K

Vibrational characterization of the compound (C2H5NH3)2PdCl4(EAPdC)

The NIR and IR transmission spectra at room temperature of single crystals of (C2H5NH3)2PdCl4 (EAPdC) have been measured, as well as unpolarized Raman spectra at room and liquid-nitrogen temperature. These vibration spectra are compared with those of EACuC and EACdC. We conclude that EAPdC belongs to the family of compounds EAMC, where M = Mn, Cu, Cd