Search for lowest-energy structure of Zintl dianion Si12 2-, Ge12 2-, and Sn12 2-

Nan Shao, Satya Bulusu, X. C. Zeng

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

We perform an unbiased search for the lowest-energy structures of Zintl dianions (Si12 2-, Ge12 2-, and Sn12 2-), by using the basin-hopping (BH) global optimization method combined with density functional theory geometric optimization. High-level ab initio calculation at the coupled-cluster level is used to determine relative stabilities and energy ranking among competitive low-lying isomers of the dianions obtained from the BH search. For Si12 2-, all BH searches (based on independent initial structures) lead to the same lowest-energy structure Si 12a 2-, a tricapped trigonal prism (TTP) with Cs group symmetry. Coupled-cluster calculation, however, suggests that another TTP isomer of Si 12c 2- is nearly isoenergetic with Si 12a 2-. For Sn12 2-, all BH searches lead to the icosahedral structure Ih - Sn 12a 2-, i.e., the stannaspherene. For Ge12 2-, however, most BH searches lead to the TTP-containing Ge 12b 2-, while a few BH searches lead to the empty-cage icosahedral structure Ih - Ge 12a 2- (named as germaniaspherene). High-level ab initio calculation indicates that Ih - Ge 12a 2- and TTP-containing Ge 12b 2- are almost isoenergetic and, thus, both may be considered as candidates for the lowest-energy structure at 0 K. Ge 12a 2- has a much larger energy gap (2.04 eV) between highest occupied molecular orbital and lowest unoccupied molecular orbital than Ge 12b 2- (1.29 eV), while Ge 12b 2- has a lower free energy than Ih - Ge 12a 2- at elevated temperature (>980 K). The TTP-containing Si 12a 2- and Ge 12b 2- exhibit large negative nuclear independent chemical shift (NICS) value (∼-44) at the center of TTP, indicating aromatic character. In contrast, germaniaspherene Ih - Ge 12a 2- and stannaspherene Ih - Sn 12a 2- exhibit modest positive NICS values, ∼12 and 3, respectively, at the center of the empty cage, indicating weakly antiaromatic character.

Original languageEnglish (US)
Article number154326
JournalJournal of Chemical Physics
Volume128
Issue number15
DOIs
StatePublished - Apr 28 2008

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Prisms
prisms
Chemical shift
Molecular orbitals
Isomers
chemical equilibrium
energy
molecular orbitals
isomers
optimization
ranking
Global optimization
Free energy
Density functional theory
Energy gap
free energy
density functional theory
symmetry
Temperature

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Search for lowest-energy structure of Zintl dianion Si12 2-, Ge12 2-, and Sn12 2-. / Shao, Nan; Bulusu, Satya; Zeng, X. C.

In: Journal of Chemical Physics, Vol. 128, No. 15, 154326, 28.04.2008.

Research output: Contribution to journalArticle

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title = "Search for lowest-energy structure of Zintl dianion Si12 2-, Ge12 2-, and Sn12 2-",
abstract = "We perform an unbiased search for the lowest-energy structures of Zintl dianions (Si12 2-, Ge12 2-, and Sn12 2-), by using the basin-hopping (BH) global optimization method combined with density functional theory geometric optimization. High-level ab initio calculation at the coupled-cluster level is used to determine relative stabilities and energy ranking among competitive low-lying isomers of the dianions obtained from the BH search. For Si12 2-, all BH searches (based on independent initial structures) lead to the same lowest-energy structure Si 12a 2-, a tricapped trigonal prism (TTP) with Cs group symmetry. Coupled-cluster calculation, however, suggests that another TTP isomer of Si 12c 2- is nearly isoenergetic with Si 12a 2-. For Sn12 2-, all BH searches lead to the icosahedral structure Ih - Sn 12a 2-, i.e., the stannaspherene. For Ge12 2-, however, most BH searches lead to the TTP-containing Ge 12b 2-, while a few BH searches lead to the empty-cage icosahedral structure Ih - Ge 12a 2- (named as germaniaspherene). High-level ab initio calculation indicates that Ih - Ge 12a 2- and TTP-containing Ge 12b 2- are almost isoenergetic and, thus, both may be considered as candidates for the lowest-energy structure at 0 K. Ge 12a 2- has a much larger energy gap (2.04 eV) between highest occupied molecular orbital and lowest unoccupied molecular orbital than Ge 12b 2- (1.29 eV), while Ge 12b 2- has a lower free energy than Ih - Ge 12a 2- at elevated temperature (>980 K). The TTP-containing Si 12a 2- and Ge 12b 2- exhibit large negative nuclear independent chemical shift (NICS) value (∼-44) at the center of TTP, indicating aromatic character. In contrast, germaniaspherene Ih - Ge 12a 2- and stannaspherene Ih - Sn 12a 2- exhibit modest positive NICS values, ∼12 and 3, respectively, at the center of the empty cage, indicating weakly antiaromatic character.",
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N2 - We perform an unbiased search for the lowest-energy structures of Zintl dianions (Si12 2-, Ge12 2-, and Sn12 2-), by using the basin-hopping (BH) global optimization method combined with density functional theory geometric optimization. High-level ab initio calculation at the coupled-cluster level is used to determine relative stabilities and energy ranking among competitive low-lying isomers of the dianions obtained from the BH search. For Si12 2-, all BH searches (based on independent initial structures) lead to the same lowest-energy structure Si 12a 2-, a tricapped trigonal prism (TTP) with Cs group symmetry. Coupled-cluster calculation, however, suggests that another TTP isomer of Si 12c 2- is nearly isoenergetic with Si 12a 2-. For Sn12 2-, all BH searches lead to the icosahedral structure Ih - Sn 12a 2-, i.e., the stannaspherene. For Ge12 2-, however, most BH searches lead to the TTP-containing Ge 12b 2-, while a few BH searches lead to the empty-cage icosahedral structure Ih - Ge 12a 2- (named as germaniaspherene). High-level ab initio calculation indicates that Ih - Ge 12a 2- and TTP-containing Ge 12b 2- are almost isoenergetic and, thus, both may be considered as candidates for the lowest-energy structure at 0 K. Ge 12a 2- has a much larger energy gap (2.04 eV) between highest occupied molecular orbital and lowest unoccupied molecular orbital than Ge 12b 2- (1.29 eV), while Ge 12b 2- has a lower free energy than Ih - Ge 12a 2- at elevated temperature (>980 K). The TTP-containing Si 12a 2- and Ge 12b 2- exhibit large negative nuclear independent chemical shift (NICS) value (∼-44) at the center of TTP, indicating aromatic character. In contrast, germaniaspherene Ih - Ge 12a 2- and stannaspherene Ih - Sn 12a 2- exhibit modest positive NICS values, ∼12 and 3, respectively, at the center of the empty cage, indicating weakly antiaromatic character.

AB - We perform an unbiased search for the lowest-energy structures of Zintl dianions (Si12 2-, Ge12 2-, and Sn12 2-), by using the basin-hopping (BH) global optimization method combined with density functional theory geometric optimization. High-level ab initio calculation at the coupled-cluster level is used to determine relative stabilities and energy ranking among competitive low-lying isomers of the dianions obtained from the BH search. For Si12 2-, all BH searches (based on independent initial structures) lead to the same lowest-energy structure Si 12a 2-, a tricapped trigonal prism (TTP) with Cs group symmetry. Coupled-cluster calculation, however, suggests that another TTP isomer of Si 12c 2- is nearly isoenergetic with Si 12a 2-. For Sn12 2-, all BH searches lead to the icosahedral structure Ih - Sn 12a 2-, i.e., the stannaspherene. For Ge12 2-, however, most BH searches lead to the TTP-containing Ge 12b 2-, while a few BH searches lead to the empty-cage icosahedral structure Ih - Ge 12a 2- (named as germaniaspherene). High-level ab initio calculation indicates that Ih - Ge 12a 2- and TTP-containing Ge 12b 2- are almost isoenergetic and, thus, both may be considered as candidates for the lowest-energy structure at 0 K. Ge 12a 2- has a much larger energy gap (2.04 eV) between highest occupied molecular orbital and lowest unoccupied molecular orbital than Ge 12b 2- (1.29 eV), while Ge 12b 2- has a lower free energy than Ih - Ge 12a 2- at elevated temperature (>980 K). The TTP-containing Si 12a 2- and Ge 12b 2- exhibit large negative nuclear independent chemical shift (NICS) value (∼-44) at the center of TTP, indicating aromatic character. In contrast, germaniaspherene Ih - Ge 12a 2- and stannaspherene Ih - Sn 12a 2- exhibit modest positive NICS values, ∼12 and 3, respectively, at the center of the empty cage, indicating weakly antiaromatic character.

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