Related Experiment Videos
Mg@C72 MNDO/d evaluation of the isomeric composition
Z Slanina1, X Zhao, X Grabuleda
1Laboratories of Computational Chemistry and Fullerene Science, Department of Knowledge-Based Information Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Aichi, Japan. slanina@cochem2.tutkie.tut.ac.jp
Journal of Molecular Graphics & Modelling
|June 8, 2001
Summary
This study computed the relative stabilities of magnesium metallofullerene Mg@C72 isomers using the MNDO/d method. Results indicate that Mg@C72 likely exists as a mixture of isomers, with the exact composition depending on preparation temperature.
Area of Science:
- Computational chemistry
- Materials science
- Nanotechnology
Background:
- Fullerenes are allotropes of carbon with unique cage-like structures.
- Metallofullerenes, where metal atoms are encapsulated within fullerene cages, exhibit novel properties.
- The stability and isomeric distribution of metallofullerenes are crucial for their synthesis and application.
Purpose of the Study:
- To compute the temperature-dependent relative stabilities of different magnesium metallofullerene Mg@C72 isomers.
- To predict the isomeric composition of Mg@C72 under varying synthesis temperatures.
- To investigate the role of enthalpy-entropy interplay in the stability of fullerene isomers.
Main Methods:
- Utilized the recently introduced Modified Neglect of Diatomic Overlap with d-functions (MNDO/d) computational method.
- Calculated potential energies for four distinct Mg@C72 isomers: one isolated-pentagon-rule (IPR) structure, two with adjacent pentagons, and one with a heptagon.
- Incorporated entropy contributions evaluated via MNDO/d-based partition functions to determine relative concentrations.
Main Results:
- The isolated-pentagon-rule (IPR) structure of Mg@C72 exhibits the lowest potential energy.
- Two isomers featuring a pair of adjacent pentagons are nearly as stable as the IPR structure.
- A structure containing a heptagon is energetically unfavorable for isolation.
- At approximately 1000 K, a mixture of two Mg@C72 isomers is predicted.
- At approximately 2000 K, three Mg@C72 isomers are predicted to have significant relative concentrations.
Conclusions:
- The isolated-pentagon-rule structure is the most stable isomer of Mg@C72.
- The isomeric distribution of Mg@C72 is temperature-dependent due to enthalpy-entropy interplay.
- Computational predictions suggest Mg@C72, if isolated, would likely be a mixture of two or three isomers.