He and N Encapsulations in Small Cages: Model Computations for Possible Nanotechnology Systems

Slanina, Zdeněk; Chow, Tahsin J.

doi:10.1166/jnn.2003.166

Cited by 7 publications

(11 citation statements)

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“…For most of the clusters, the calculated Δ r H values are negative, indicating the exothermic nature of the encapsulation process. It is interesting to note that the calculated Δ r G and Δ r H values of some of the experimentally observed 8−10 endohedral metallofullerene systems such as U@C 28 and Ti@C 28 are found to be comparable to that of the U@C 36 cluster using the same level of theory. Thus, the calculated Δ r G (Δ r H) values are found to be −673 (−722) and −541 (−548) kJ/mol for the U@C 28 and Ti@C 28 systems, respectively.…”

Section: Resultsmentioning

confidence: 91%

“…It is interesting to note that the calculated Δ r G and Δ r H values of some of the experimentally observed 8−10 endohedral metallofullerene systems such as U@C 28 and Ti@C 28 are found to be comparable to that of the U@C 36 cluster using the same level of theory. Thus, the calculated Δ r G (Δ r H) values are found to be −673 (−722) and −541 (−548) kJ/mol for the U@C 28 and Ti@C 28 systems, respectively. These values are comparable to the Δ r G and Δ r H values reported in the present work for the most stable U@C 36 system.…”

Section: Resultsmentioning

confidence: 91%

“…The triplet and quintet Str-01-C 6v isomers are found to be energetically less stable by 14.1 and 71.7 kcal/mol, respectively, as compared to the most stable singlet Str-01-C 6v U@C 36 cluster (cf., 7.5 and 50.3 kcal/mol with B3LYP functional). Now it is interesting to investigate the structural transitions of the C 36 cage during encapsulation of a U atom, the way it is done for the Ti@C 28 79 system in a recent theoretical report. For that purpose, we have started the geometry optimization process by placing the U atom on the center position of the various bare C 36 cages, associated with different symmetries.…”

Section: Resultsmentioning

confidence: 99%

“…However, recently some of the endohedral C 36 systems X@C 36 (X = He, N, C, H, Li, Na, K) are investigated theoretically. 27,28,31,34 In this work, we mainly consider different classical cage structures of C 36 with different symmetries along with ring and bowl isomers, 13,29 and investigate the possibility of further stabilization of C 36 isomers through encapsulation of a uranium atom. To the best of our knowledge, actinide atom encapsulated C 36 fullerene, in particular, U@C 36 , has not been investigated theoretically, although experimental evidence indicates the possible existence of this system.…”

Section: Introductionmentioning

confidence: 99%

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Enhancement in the Stability of 36-Atom Fullerene through Encapsulation of a Uranium Atom

Manna

Ghanty

2013

J. Phys. Chem. C

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With an objective to rationalize the experimentally observed intense U@C 36 peak in the mass spectrum of U@C 2n metallofullerene, structural, stability, and spectroscopic aspects of the uranium doped C 36 fullerene have been studied in a unified and systematic way using density functional theory (DFT) and its time-dependent variant. Relativistic effects have been taken into account within the framework of zeroth-order regular approximation using scalar and spin− orbit-based approaches. Among all of the 15 possible classical isomers reported for the C 36 fullerene cage system, singlet D 2d and triplet D 6h structures are found to be isoenergetic and most stable. Encapsulation of uranium atom into various C 36 cages leads to 15 distinct isomers with considerable energy differences. It has also been shown that this encapsulation process results in significant gain in thermodynamic stability. The most stable U@C 36 isomer is found to be associated with C 6v symmetry and closed-shell electronic configuration, derived from the open-shell D 6h structure of C 36 . The next stable isomer is associated with C s symmetry and obtained from the corresponding singlet D 2d structure of the C 36 cage. Distinct changes have also been found in the calculated vibrational and UV−visible spectra of the U@C 36 cluster as compared to the corresponding bare C 36 cage. All of the calculated quantities reported here suggest that the stability of the U@C 36 cluster is high enough for possible formation of cluster-assembled material leading to synthesis of this metallofullerene experimentally.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enhancement in the Stability of 36-Atom Fullerene through Encapsulation of a Uranium Atom

Manna

Ghanty

2013

J. Phys. Chem. C

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“…There is also a few theoretical studies of N@C n systems. For instance, semiempirical 10, 11 and ab initio (HF) 11 calculations of the N@C n systems were carried out. The results of MNDO/AM1 calculations sug gested the possibility for endohedral compounds of C 34 and C 36 fullerenes (D 2d , D 3h and C 2v isomers of C 36 were considered) with nitrogen to exist.…”

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confidence: 99%

Quantum chemical calculations of N@Cn endofullerenes (n ≤ 60)

2006

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The geometric parameters and energy characteristics of small endofullerenes N@C n (n = 20, 24, 30, 32, 40, 50) and N@C 60 in the quartet ground state were calculated by the B3LYP/6 31G* method. The N atom is located at the center of the carbon cage in all mol ecules except N@C 30 , where it is bound to the cage wall. Encapsulation of nitrogen atom has little effect on the fullerene cage geometry for n = 40, 50, and 60. No significant charge transfer from the N endo atom to the cage was revealed for all the N@C n endofullerenes studied. The calculated spin density on the nitrogen endo atom increases as the size (n) of the carbon cage increases. The relative stabilities of C n fullerenes and corresponding endofullerenes N@C n are discussed.The synthesis and investigation of endofullerenes have been attracting increasing attention of researchers; 1 how ever, most studies in this field are concerned with endo hedral compounds of higher fullerenes C n (n > 60). A large number of endohedral compounds with rare gases, 1 metals, 1 and nitrogen and phosphorus atoms 2,3 were ob tained and studied. Of particular interest is the N@C 60 endofullerene, because experiments revealed an unexpect edly large value of the hyperfine coupling (HFC) con stant on the endo atom compared to free nitrogen atom. 2 Both experiment and theory (see Refs 2 and 4-7) show that in this molecule the nitrogen atom is located at the center of the fullerene cage and retains its initial elec tronic configuration (...2p 3 ). Endohedral compounds of small fullerenes C n (n < 60)* with nitrogen have not been synthesized as yet. There is also a few theoretical studies of N@C n systems. For instance, semiempirical 10,11 and ab initio (HF) 11 calculations of the N@C n systems were carried out. The results of MNDO/AM1 calculations sug gested the possibility for endohedral compounds of C 34 and C 36 fullerenes (D 2d , D 3h and C 2v isomers of C 36 were considered) with nitrogen to exist.

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