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Panchagnula K, Graf D, Johnson ER, Thom AJW. Targeting spectroscopic accuracy for dispersion bound systems from ab initio techniques: Translational eigenstates of Ne@C70. J Chem Phys 2024; 161:054308. [PMID: 39092939 DOI: 10.1063/5.0223298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 07/17/2024] [Indexed: 08/04/2024] Open
Abstract
We investigate the endofullerene system Ne@C70 by constructing a three-dimensional Potential Energy Surface (PES) describing the translational motion of the Ne atom. This is constructed from electronic structure calculations from a plethora of methods, including MP2, SCS-MP2, SOS-MP2, RPA@PBE, and C(HF)-RPA, which were previously used for He@C60 in Panchagnula et al. [J. Chem. Phys. 160, 104303 (2024)], alongside B86bPBE-25X-XDM and B86bPBE-50X-XDM. The reduction in symmetry moving from C60 to C70 introduces a double well potential along the anisotropic direction, which forms a test of the sensitivity and effectiveness of the electronic structure methods. The nuclear Hamiltonian is diagonalized using a symmetrized double minimum basis set outlined in Panchagnula and Thom [J. Chem. Phys. 159, 164308 (2023)], with translational energies having error bars ±1 and ±2 cm-1. We find no consistency between electronic structure methods as they find a range of barrier heights and minima positions of the double well and different translational eigenspectra, which also differ from the Lennard-Jones (LJ) PES given in Mandziuk and Bačić [J. Chem. Phys. 101, 2126-2140 (1994)]. We find that generating effective LJ parameters for each electronic structure method cannot reproduce the full PES nor recreate the eigenstates, and this suggests that the LJ form of the PES, while simple, may not be best suited to describe these systems. Even though MP2 and RPA@PBE performed best for He@C60, due to the lack of concordance between all electronic structure methods, we require more experimental data in order to properly validate the choice.
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Affiliation(s)
- K Panchagnula
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - D Graf
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- Department of Chemistry, University of Munich (LMU), Munich, Germany
| | - E R Johnson
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- Department of Chemistry, Dalhousie University, 6243 Alumni Crescent, Halifax, Nova Scotia B3H 4R2, Canada
| | - A J W Thom
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
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2
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Ma S, Hester BR, Lloyd AJ, dos Santos AM, Molaison JJ, Wilkinson AP. Synthesis and Properties of the Helium Clathrate and Defect Perovskite [He 2-x □ x ][CaNb]F 6. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:11006-11013. [PMID: 38983596 PMCID: PMC11229063 DOI: 10.1021/acs.jpcc.4c02174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Revised: 06/04/2024] [Accepted: 06/14/2024] [Indexed: 07/11/2024]
Abstract
The defect double perovskite [He2-x □ x ][CaNb]F6, with helium on its A-site, can be prepared by the insertion of helium into ReO3-type CaNbF6 at high pressure. Upon cooling from 300 to 100 K under 0.4 GPa helium, ∼60% of the A-sites become occupied. Helium uptake was quantified by both neutron powder diffraction and gas insertion and release measurements. After the conversion of gauge pressure to fugacity, the uptake of helium by CaNbF6 can be described by a Langmuir isotherm. The enthalpy of absorption for helium in [He2-x □ x ][CaNb]F6 is estimated to be ∼+3(1) kJ mol-1, implying that its formation is entropically favored. Helium is able to diffuse through the material on a time scale of minutes at temperatures down to ∼150 K but is trapped at 100 K and below. The insertion of helium into CaNbF6 reduces the magnitude of its negative thermal expansion, increases the bulk modulus, and modifies its phase behavior. On compressing pristine CaNbF6, at 50 and 100 K, a cubic (Fm3̅m) to rhombohedral (R3̅) phase transition was observed at <0.20 GPa. However, a helium-containing sample remained cubic at 0.4 GPa and 50 K. CaNbF6, compressed in helium at room temperature, remained cubic to >3.7 GPa, the limit of our X-ray diffraction measurements, in contrast to prior reports that upon compression in a nonpenetrating medium, a phase transition is detected at ∼0.4 GPa.
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Affiliation(s)
- Shangye Ma
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, Atlanta, Georgia 30332-0400, United States
| | - Brett R. Hester
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, Atlanta, Georgia 30332-0400, United States
| | - Anthony J. Lloyd
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, Atlanta, Georgia 30332-0400, United States
| | - Antonio M. dos Santos
- Neutron
Scattering Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jamie J. Molaison
- Neutron
Scattering Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Angus P. Wilkinson
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, Atlanta, Georgia 30332-0400, United States
- School
of Materials Science and Engineering, Georgia
Institute of Technology, Atlanta, Georgia 30332-0245, United States
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3
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Ajibade S, Catalano L, Kölbel J, Mittleman DM, Ruggiero MT. Terahertz Spectroscopy Unambiguously Determines the Orientation of Guest Water Molecules in a Structurally Elusive Metal-Organic Framework. J Phys Chem Lett 2024; 15:5549-5555. [PMID: 38753602 PMCID: PMC11129291 DOI: 10.1021/acs.jpclett.4c00706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/19/2024] [Accepted: 04/26/2024] [Indexed: 05/18/2024]
Abstract
Porous materials, particularly metal-organic frameworks (MOFs), hold great promise for advanced applications. MIL-53(Al) is an exceptionally well-studied MOF that exhibits a phase transition upon guest capture─in this case, water─resulting in a dramatic change in the pore volume. Despite extensive studies, the structure of the water-loaded narrow-pore phase, MIL-53(Al)-np, remains controversial, particularly with respect to the positions of the adsorbed water molecules. We use terahertz spectroscopy, coupled with powder X-ray diffraction and density functional theory simulations, to unambiguously resolve this controversy. We show that the low-frequency (<100 cm-1) vibrational spectrum depends on weak long-range forces that are extremely sensitive to the orientation of the adsorbed water molecules. This enables definitively determining the correct structure of MIL-53(Al)-np while highlighting the extreme sensitivity of terahertz spectroscopy to bulk structure, suggesting its potential as a robust complement to X-ray diffraction for precise characterization of host-guest complexes.
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Affiliation(s)
- Saheed
A. Ajibade
- Department
of Chemistry, University of Vermont, Burlington, Vermont 05405, United States
| | - Luca Catalano
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
- Department
of Life Sciences, University of Modena and
Reggio Emilia, 41125 Modena, Italy
| | - Johanna Kölbel
- School
of Engineering, Brown University, Providence, Rhode Island 02912, United States
| | - Daniel M. Mittleman
- School
of Engineering, Brown University, Providence, Rhode Island 02912, United States
| | - Michael T. Ruggiero
- Department
of Chemistry, University of Vermont, Burlington, Vermont 05405, United States
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Vyas VK, Bacanu GR, Soundararajan M, Marsden ES, Jafari T, Shugai A, Light ME, Nagel U, Rõõm T, Levitt MH, Whitby RJ. Squeezing formaldehyde into C 60 fullerene. Nat Commun 2024; 15:2515. [PMID: 38514674 PMCID: PMC10957948 DOI: 10.1038/s41467-024-46886-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Accepted: 03/13/2024] [Indexed: 03/23/2024] Open
Abstract
The cavity inside fullerene C60 provides a highly symmetric and inert environment for housing atoms and small molecules. Here we report the encapsulation of formaldehyde inside C60 by molecular surgery, yielding the supermolecular complex CH2O@C60, despite the 4.4 Å van der Waals length of CH2O exceeding the 3.7 Å internal diameter of C60. The presence of CH2O significantly reduces the cage HOMO-LUMO gap. Nuclear spin-spin couplings are observed between the fullerene host and the formaldehyde guest. The rapid spin-lattice relaxation of the formaldehyde 13C nuclei is attributed to a dominant spin-rotation mechanism. Despite being squeezed so tightly, the encapsulated formaldehyde molecules rotate freely about their long axes even at cryogenic temperatures, allowing observation of the ortho-to-para spin isomer conversion by infrared spectroscopy. The particle in a box nature of the system is demonstrated by the observation of two quantised translational modes in the cryogenic THz spectra.
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Affiliation(s)
- Vijyesh K Vyas
- School of Chemistry, University of Southampton, SO17 1BJ, Southampton, UK
| | - George R Bacanu
- School of Chemistry, University of Southampton, SO17 1BJ, Southampton, UK
| | | | | | - Tanzeeha Jafari
- National Institute of Chemical Physics and Biophysics, Akademia tee 23, 12618, Tallinn, Estonia
- Department of Cybernetics, Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia
| | - Anna Shugai
- National Institute of Chemical Physics and Biophysics, Akademia tee 23, 12618, Tallinn, Estonia
| | - Mark E Light
- School of Chemistry, University of Southampton, SO17 1BJ, Southampton, UK
| | - Urmas Nagel
- National Institute of Chemical Physics and Biophysics, Akademia tee 23, 12618, Tallinn, Estonia
| | - Toomas Rõõm
- National Institute of Chemical Physics and Biophysics, Akademia tee 23, 12618, Tallinn, Estonia.
| | - Malcolm H Levitt
- School of Chemistry, University of Southampton, SO17 1BJ, Southampton, UK.
| | - Richard J Whitby
- School of Chemistry, University of Southampton, SO17 1BJ, Southampton, UK.
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Panchagnula K, Graf D, Albertani FEA, Thom AJW. Translational eigenstates of He@C60 from four-dimensional ab initio potential energy surfaces interpolated using Gaussian process regression. J Chem Phys 2024; 160:104303. [PMID: 38465682 DOI: 10.1063/5.0197903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Accepted: 02/22/2024] [Indexed: 03/12/2024] Open
Abstract
We investigate the endofullerene system 3He@C60 with a four-dimensional potential energy surface (PES) to include the three He translational degrees of freedom and C60 cage radius. We compare second order Møller-Plesset perturbation theory (MP2), spin component scaled-MP2, scaled opposite spin-MP2, random phase approximation (RPA)@Perdew, Burke, and Ernzerhof (PBE), and corrected Hartree-Fock-RPA to calibrate and gain confidence in the choice of electronic structure method. Due to the high cost of these calculations, the PES is interpolated using Gaussian Process Regression (GPR), owing to its effectiveness with sparse training data. The PES is split into a two-dimensional radial surface, to which corrections are applied to achieve an overall four-dimensional surface. The nuclear Hamiltonian is diagonalized to generate the in-cage translational/vibrational eigenstates. The degeneracy of the three-dimensional harmonic oscillator energies with principal quantum number n is lifted due to the anharmonicity in the radial potential. The (2l + 1)-fold degeneracy of the angular momentum states is also weakly lifted, due to the angular dependence in the potential. We calculate the fundamental frequency to range between 96 and 110 cm-1 depending on the electronic structure method used. Error bars of the eigenstate energies were calculated from the GPR and are on the order of ∼±1.5 cm-1. Wavefunctions are also compared by considering their overlap and Hellinger distance to the one-dimensional empirical potential. As with the energies, the two ab initio methods MP2 and RPA@PBE show the best agreement. While MP2 has better agreement than RPA@PBE, due to its higher computational efficiency and comparable performance, we recommend RPA as an alternative electronic structure method of choice to MP2 for these systems.
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Affiliation(s)
- K Panchagnula
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - D Graf
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - F E A Albertani
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - A J W Thom
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
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Moncada F, Quintero W, Posada E, Pettersson LGM, Reyes A. A nuclear configuration interaction approach to study nuclear spin effects: an application to ortho- and para- 3 He 2 @C 60. Chemphyschem 2024; 25:e202300498. [PMID: 38055206 DOI: 10.1002/cphc.202300498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/29/2023] [Accepted: 12/01/2023] [Indexed: 12/07/2023]
Abstract
We introduce a non-orthogonal configuration interaction approach to investigate nuclear quantum effects on energies and densities of confined fermionic nuclei. The Hamiltonian employed draws parallels between confined systems and many-electron atoms, where effective non-Coulombic potentials represent the interactions of the trapped particles. One advantage of this method is its generality, as it offers the potential to study the nuclear quantum effects of various confined species affected by effective isotropic or anisotropic potentials. As a first application, we analyze the quantum states of two 3 He atoms encapsulated in C60 . At the Hartree-Fock level, we observe the breaking of spin and spatial symmetries. To ensure wavefunctions with the correct symmetries, we mix the broken-symmetry Hartree-Fock states within the non-orthogonal configuration interaction expansion. Our proposed approach predicts singly and triply degenerate ground states for the singlet (para-3 He2 @C60 ) and triplet (ortho-3 He2 @C60 ) nuclear spin configurations, respectively. The ortho-3 He2 @C60 ground state is 5.69 cm-1 higher in energy than the para-3 He2 @C60 ground state. The nuclear densities obtained for these states exhibit the icosahedral symmetry of the C60 embedding potential. Importantly, our calculated energies for the lowest 85 states are in close agreement with perturbation theory results based on a harmonic oscillator plus rigid rotor model of 3 He2 @C60 .
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Affiliation(s)
- Félix Moncada
- Department of Physics, AlbaNova University Center, Stockholm University, 106 91, Stockholm, Sweden
- Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 45-03, Bogotá, Colombia
| | - William Quintero
- Doctorado en Fisicoquímica Molecular, Universidad Andres Bello, Santiago de Chile, Chile
- Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 45-03, Bogotá, Colombia
| | - Edwin Posada
- Institute for Computational Molecular Science, Temple University, Philadelphia, PA, USA
- Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 45-03, Bogotá, Colombia
| | - Lars G M Pettersson
- Department of Physics, AlbaNova University Center, Stockholm University, 106 91, Stockholm, Sweden
| | - Andrés Reyes
- Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 45-03, Bogotá, Colombia
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7
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Banerjee S, Ash T, Debnath T, Das AK. Dual modification to stabilize Non-IPR C 72 fullerene: A new theoretical strategy. J Mol Graph Model 2022; 117:108289. [PMID: 35964364 DOI: 10.1016/j.jmgm.2022.108289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 07/21/2022] [Accepted: 08/01/2022] [Indexed: 01/14/2023]
Abstract
The stabilization of non-IPR fullerenes for their isolation and characterization is an area of recent interest. In the present study, we have explored the stabilization techniques of C72 isomers via endo and exo-modifications and finally approached dual modification. A total of four isomers of C72 have been considered in this study; among them, one is IPR derivative (1), and the rest are non-IPR derivatives with one (2) and two (3 and 4) fused pentagon rings. First, we have studied the endohedral modification by encapsulating one and two La atoms in the C72 cavity. Secondly, we have exohedrally modified the C72 isomers via chlorination by adding four and eight chlorides, respectively. Our final approach is to study the dual modification, where we have implemented both endo exo-modifications together. This dual modification can be achieved in two ways: exo followed by endo and endo followed by exo. For each modification, the relative stability of every modified C72 derivative has been checked by calculating the relative energy with respect to the most stable modified analogue. To find out whether these modifications are energetically feasible or not, we have calculated the binding energy of each modified C72 isomer. The binding energy calculation reveals that the encapsulation and exo-modification techniques are good enough to stabilize the non-IPR C72 derivatives. Moreover, the effectiveness of dual modification has also been established from the enhanced binding energy compared to either endo- or exo-modification. We have also studied the NPA charges on the encapsulated La atoms for each endo- and dual-modified C72 derivative. Furthermore, the AIM study has also been perceived to find out the interaction between the La atom and the fullerene cages for both mono- and di-encapsulated fullerene derivatives and also between La-La centres for di-encapsulated derivatives. Overall, the present theoretical study will provide an idea about the stability of the modified C72 derivatives, which will help the experimentalists to design new strategies for synthesizing modified non-IPR fullerene derivatives that have vast applications in the medicinal and industrial fields.
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Affiliation(s)
- Soumadip Banerjee
- School of Mathematical & Computational Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India
| | - Tamalika Ash
- School of Mathematical & Computational Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India
| | - Tanay Debnath
- School of Mathematical & Computational Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India.
| | - Abhijit K Das
- School of Mathematical & Computational Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India.
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8
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Bloodworth S, Whitby RJ. Synthesis of endohedral fullerenes by molecular surgery. Commun Chem 2022; 5:121. [PMID: 36697689 PMCID: PMC9814919 DOI: 10.1038/s42004-022-00738-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 09/21/2022] [Indexed: 01/28/2023] Open
Abstract
Encapsulation of atoms or small molecules inside fullerenes provides a unique opportunity for study of the confined species in the isolated cavity, and the synthesis of closed C60 or C70 fullerenes with enclosed atoms or molecules has recently developed using the method of 'molecular surgery'; in which an open-cage intermediate fullerene is the host for encapsulation of a guest species, before repair of the cage opening. In this work we review the main methods for cage-opening and closure, and the achievements of molecular surgery to date.
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Affiliation(s)
- Sally Bloodworth
- grid.5491.90000 0004 1936 9297Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ UK
| | - Richard J. Whitby
- grid.5491.90000 0004 1936 9297Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ UK
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Hoffman G, Bacanu GR, Marsden ES, Walkey MC, Sabba M, Bloodworth S, Tizzard GJ, Levitt MH, Whitby RJ. Synthesis and 83Kr NMR spectroscopy of Kr@C 60. Chem Commun (Camb) 2022; 58:11284-11287. [PMID: 36124877 DOI: 10.1039/d2cc03398d] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthesis of Kr@C60 is achieved by quantitative high-pressure encapsulation of the noble gas into an open-fullerene, and subsequent cage closure. Krypton is the largest noble gas entrapped in C60 using 'molecular surgery' and Kr@C60 is prepared with >99.4% incorporation of the endohedral atom, in ca. 4% yield from C60. Encapsulation in C60 causes a shift of the 83Kr resonance by -39.5 ppm with respect to free 83Kr in solution. The 83Kr spin-lattice relaxation time T1 is approximately 36 times longer for Kr encapsulated in C60 than for free Kr in solution. This is the first characterisation of a stable Kr compound by 83Kr NMR.
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Affiliation(s)
- Gabriela Hoffman
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - George R Bacanu
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Elizabeth S Marsden
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Mark C Walkey
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Mohamed Sabba
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Sally Bloodworth
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Graham J Tizzard
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Malcolm H Levitt
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
| | - Richard J Whitby
- Chemistry, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
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Jafari T, Razvan Bacanu G, Shugai A, Nagel U, Walkey M, Hoffman G, Levitt MH, Whitby RJ, Rõõm T. Terahertz spectroscopy of the helium endofullerene He@C 60. Phys Chem Chem Phys 2022; 24:9943-9952. [PMID: 35445229 DOI: 10.1039/d2cp00515h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We studied the quantized translational motion of single He atoms encapsulated in molecular cages by terahertz absorption. The temperature dependence of the THz absorption spectra of 3He@C60 and 4He@C60 crystal powder samples was measured between 5 and 220 K. At 5 K there is an absorption line at 96.8 cm-1 (2.90 THz) in 3He@C60 and at 81.4 cm (2.44 THz) in 4He@C60, while additional absorption lines appear at higher temperature. An anharmonic spherical oscillator model with a displacement-induced dipole moment was used to model the absorption spectra. Potential energy terms with powers of two, four and six and induced dipole moment terms with powers one and three in the helium atom displacement from the fullerene cage center were sufficient to describe the experimental results. Excellent agreement is found between potential energy functions derived from measurements on the 3He and 4He isotopes. One absorption line corresponds to a three-quantum transition in 4He@C60, allowed by the anharmonicity of the potential function and by the non-linearity of the dipole moment in He atom displacement. The potential energy function of icosahedral symmetry does not explain the fine structure observed in the low temperature spectra.
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Affiliation(s)
- Tanzeeha Jafari
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
| | | | - Anna Shugai
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
| | - Urmas Nagel
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
| | - Mark Walkey
- School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK
| | - Gabriela Hoffman
- School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK
| | - Malcolm H Levitt
- School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK
| | - Richard J Whitby
- School of Chemistry, University of Southampton, SO17 1BJ Southampton, UK
| | - Toomas Rõõm
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
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11
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Xu M, Felker PM, Bačić Z. H 2O inside the fullerene C 60: Inelastic neutron scattering spectrum from rigorous quantum calculations. J Chem Phys 2022; 156:124101. [PMID: 35364860 DOI: 10.1063/5.0086842] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a methodology that, for the first time, allows rigorous quantum calculation of the inelastic neutron scattering (INS) spectra of a triatomic molecule in a nanoscale cavity, in this case, H2O inside the fullerene C60. Both moieties are taken to be rigid. Our treatment incorporates the quantum six-dimensional translation-rotation (TR) wave functions of the encapsulated H2O, which serve as the spatial parts of the initial and final states of the INS transitions. As a result, the simulated INS spectra reflect the coupled TR dynamics of the nanoconfined guest molecule. They also exhibit the features arising from symmetry breaking observed for solid H2O@C60 at low temperatures. Utilizing this methodology, we compute the INS spectra of H2O@C60 for two incident neutron wavelengths and compare them with the corresponding experimental spectra. Good overall agreement is found, and the calculated spectra provide valuable additional insights.
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Affiliation(s)
- Minzhong Xu
- Department of Chemistry, New York University, New York, New York 10003, USA
| | - Peter M Felker
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
| | - Zlatko Bačić
- Department of Chemistry, New York University, New York, New York 10003, USA
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