Computational and Experimental investigation of Nalipoite-Li2APO4 (A = Na, K) electrolytes for Li-ion batteries

ABSTRACTThe potential ionic conductors Li2APO4 (A = Na, K) are investigated combining experiments and first principles calculations at the Density Functional Theory level. A high ionic conductivity of 6.5 x10−6 and 1.5 x10−5 S cm−1 at 25 and 70°C, respectively, is found in Nalipoite-Li2NaPO4. For this mixed phosphate the energy barriers to Li motion are calculated. The lower energy barrier (0.7 eV) implies the inter-chain diffusion of Li in the b-c plane. We predict that ionic mobility is enhanced in the isostructural Li2KPO4, with the lowest calculated energy barrier being 0.4 eV.

DFT STUDY OF THE FORMATION OF CH2=CF2 THROUGH BOTH METHYLENE INSERTION AND β-FLUORIDE ELIMINATION ON THE Ag(111) SURFACE

Total energy calculations based on (1) density functional theory (DFT) in connection with ultrasoft pseudopotential and generalized gradient spin-polarized approximation (GGSA) and (2) the partial structural constraint path minimization (PSCPM) method have been used to investigate the energetically more favorable pathway for methylene ( CH 2) insertion into the Ag–CF 3 bond followed by β-fluoride elimination to generate an isolated CH 2= CF 2( g ) above the Ag(111) surface. The diffusion of the fcc-hollow site of CF 3( ads ) toward the bridge site of CH 2( ads ) is proposed as an energe*tically more favorable path for CH 2 insertion into the Ag–CF 3 bond to form the bridge site of CH 2 CF 3( ads ) on the Ag(111) surface. Then we proceed with β-fluoride elimination to form an isolated CH 2= CF 2( g ) and the bridge site of F (ads) on the Ag(111) surface. Our calculated energy barrier for β-fluoride elimination is 0.715 eV higher than that for CH 2 insertion on the Ag(111) surface. These calculated results imply that β-fluoride elimination rather than CH 2 insertion on the Ag(111) surface controls the CH 2= CF 2( g ) formation rate as observed from temperature-programmed reaction (TPR) experimental data. Finally, we attribute these different energy barriers to the different transition state structures — largely distorted seven-centered versus less distorted four-centered — involved in these two different processes.

Ab Initio Study of Conformational Properties of (Z,Z,Z)-Cyclonona-1,3,6-Triene

Ab initio molecular orbital and density functional theory (DFT) calculations, applied to ( Z,Z,Z)-cyclonona-1,3,6-triene (1) have revealed that the calculated energy barrier for ring inversion of the twist-boat ( C1 symmetry) conformation of 1 as a most stable form is 8.41 kcal mol−1, as calculated by the MP2/6-31G*//HF/6-31G* method

AM1 Study of the Conformational Properties of (Z,Z)-Cyclonona-1,3-diene

The unsymmetrical boat-chair BC conformation of ( Z,Z)-cyclonona-1,3-diene is calculated to be 5 kJ mol−1 more stable than the axial-symmetrical twist-boat-chair TBC form; while the calculated energy barrier for limited pseudorotation of BC and TBC is only 10.2kJ mol−1, ring inversion of BC via plane-symmetrical boat geometry requires 24.4 kJ mol−1.