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Sc 3 N@C 80 : Computations on the Two‐Isomer Equilibrium at High Temperatures
Author(s) -
Slanina Zdeněk,
Nagase Shigeru
Publication year - 2005
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400655
Subject(s) - gibbs free energy , chemistry , population , thermodynamics , crystallography , physics , demography , sociology
Reported herein are computations on the relative concentrations of the two experimentally known isomers of Sc 3 N@C 80 , that is, those produced by encapsulation of Sc 3 N in two particular C 80 cages that obey the isolated‐pentagon rule, namely, with I h and D 5 h symmetries. The calculations are based on density functional methods and have been carried out using the Gibbs energy over a broad temperature interval. It has been computed that, if a relatively free motion of the encapsulate inside the cages is allowed, the observed populations of 10 and 17 % for the D 5 h Sc 3 N@C 80 species are reached at temperatures of 2100 and 2450 K, respectively. The inclusion of the entropy term is essential as, if it is neglected, the D 5 h Sc 3 N@C 80 population at a temperature of 2100 K would be a mere 1 %, owing to the relatively large interisomeric separation potential energy of 19 kcal mol −1 .