calculated energy barrier
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2015 ◽  
Vol 1740 ◽  
Author(s):  
G. F. Ortiz ◽  
M C. López ◽  
M.E. Arroyo-de Dompablo ◽  
José L. Tirado

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.



2004 ◽  
Vol 11 (02) ◽  
pp. 229-234 ◽  
Author(s):  
JYH SHING LIN ◽  
WEN-CHI CHOU

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.



2003 ◽  
Vol 2003 (9) ◽  
pp. 546-548
Author(s):  
Davood Nori-Shargh ◽  
Mostafa Mohammadpour Amini ◽  
Saeed Jameh-Bozorghi ◽  
Nooshin Heydari laalee

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



1999 ◽  
Vol 23 (10) ◽  
pp. 616-617
Author(s):  
Issa Yavari ◽  
Hassan Norouzi-Arasi ◽  
Hossain Fallah-Bagher-Shaidaei

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.



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