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Prosmiti R, González-Lezana T. Computational Modeling: Up-to-Date Approaches and Cutting-Edge Applications from Clusters, Nanostructures to Bulk Systems. Chemphyschem 2024; 25:e202400207. [PMID: 38837591 DOI: 10.1002/cphc.202400207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Indexed: 06/07/2024]
Abstract
The contributions in this special theme collection, in honor to Prof. P. Villarreal, cover a broad variety of computational methodologies and experimental techniques, containing studies on gas phase, clusters and condensed phase systems.
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Affiliation(s)
- Rita Prosmiti
- Instituto de Fìsica Fundamental, IFF-CSIC, Serrano 123, 28006, Madrid, Spain
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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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de Lara-Castells MP, Mitrushchenkov AO. A nuclear spin and spatial symmetry-adapted full quantum method for light particles inside carbon nanotubes: clusters of 3He, 4He, and para-H2. Phys Chem Chem Phys 2021; 23:7908-7918. [DOI: 10.1039/d0cp05332e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new nuclear spin and spatial symmetry-adapted full quantum method for light fermionic and bosonic particles under cylindrical carbon nanotube confinement.
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Valdés Á, Prosmiti R. Quantum effects on the stability of the He 5 I 2 van der Waals conformers. J Comput Chem 2019; 40:2200-2206. [PMID: 31148224 DOI: 10.1002/jcc.25870] [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: 01/11/2019] [Revised: 04/10/2019] [Accepted: 05/16/2019] [Indexed: 11/05/2022]
Abstract
We present 15-dimensional quantum multiconfiguration time-dependent Hartree calculations of the vibrational levels of the He5 I2 van der Waals (vdW) complex employing an ab initio-based potential energy surface (PES). The energies and spatial features of such bound structures are analyzed, providing predictions on the structures and relative stabilities of its three lowest isomers. We found that the most stable isomer corresponds to all five He atoms encircling the I2 molecule, indicating that in this case the anharmonic quantum effects do not stabilize the isomers involving a He atom in a linear configuration as reported previously for the smaller HeN I2 systems. Such finding provides information on the overall structuring of the finite-size-solvent systems, highlighting the intriguing interplay between weak intermolecular interactions and quantum effects. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Álvaro Valdés
- Departamento de Física, Universidad Nacional de Colombia, Calle 26, Cra 39, Edificio 404, Bogotá, Colombia
| | - Rita Prosmiti
- Departamento PAMS, Instituto de Física Fundamental (IFF-CSIC), CSIC, Serrano 123, 28006, Madrid, Spain
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Rodríguez-Cantano R, González-Lezana T, Villarreal P. Path integral Monte Carlo investigations on doped helium clusters. INT REV PHYS CHEM 2016. [DOI: 10.1080/0144235x.2015.1132595] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Modesto-Costa L, Canuto S, Mukherjee PK, Fricke B. A simple model for a theoretical study of the spectral line shifts of alkali atoms attached to helium nanodroplets. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2015.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Villarreal P, Rodríguez-Cantano R, González-Lezana T, Prosmiti R, Delgado-Barrio G, Gianturco FA. Quantum Features of Anionic Species He*⁻ and He₂*⁻ in Small He(N) Clusters. J Phys Chem A 2015; 119:11574-82. [PMID: 26517581 DOI: 10.1021/acs.jpca.5b08470] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present variational calculations on systems containing a few boson helium atoms attached to electronically excited atomic and molecular helium anions He*⁻ and He₂*⁻ and characterize their structures and energetics. Previously reported high-level ab initio results [Huber, S. E.; Mauracher, A. Mol. Phys. 2014, 112, 794] to describe the interactions between excited (metastable) anions and a neutral He atom have been employed. For the case of the atomic species He*⁻, the corresponding interaction with He suggests large anharmonicity effects due to the presence of a deep well of ∼17,500 cm⁻¹ at short distances, together with a more external shallow secondary well of ∼4 cm⁻¹, both supporting bound levels. Moreover, when a sum of pairwise interactions is assumed to describe the full PES corresponding to the presence of several neutral He atoms, geometrical constraints already predict the complete solvation of the anionic impurity by six helium atoms, giving rise to a bipyramidal structure. In turn, for the anisotropic weak interaction He-He₂*⁻, where the anionic dimer is considered as a rigid rotor, the obtained structures show the tendency of the helium atoms to pack themselves together and largely far away from the dopant, thereby confirming the heliophobic character of He₂*⁻.
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Affiliation(s)
- Pablo Villarreal
- Instituto de Fı́sica Fundamental, IFF-CSIC , Serrano 123, 28006 Madrid, Spain
| | | | | | - Rita Prosmiti
- Instituto de Fı́sica Fundamental, IFF-CSIC , Serrano 123, 28006 Madrid, Spain
| | | | - Franco A Gianturco
- Institute of Ion Physics, The University of Innsbruck , Technikerstrasse 25, 6020 Innsbruck, Austria.,Scuola Normale Superiore ,Piazza dei Cavalieri 7, 56126 Pisa, Italy
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Aguirre NF, Villarreal P, Delgado-Barrio G, Posada E, Reyes A, Biczysko M, Mitrushchenkov AO, de Lara-Castells MP. Including nuclear quantum effects into highly correlated electronic structure calculations of weakly bound systems. J Chem Phys 2013; 138:184113. [DOI: 10.1063/1.4803546] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Aguirre NF, Villarreal P, Delgado-Barrio G, Mitrushchenkov AO, de Lara-Castells MP. Solvent states and spectroscopy of doped helium clusters as a quantum-chemistry-like problem. Phys Chem Chem Phys 2013; 15:10126-40. [DOI: 10.1039/c3cp50282a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Unravelling Coriolis temperature-dependent effects on doped helium clusters: Vib-rotational Raman spectra of (3,4He)4–Cl2(X). Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2012.10.048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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11
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Structure and dynamics of noble gas-halogen and noble gas ionic clusters: When theory meets experiment. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2011.05.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Villarreal P, Miret-Artés S, Roncero O, Campos-Martínez J. New trends in atomic and molecular clusters (in honour of Gerardo Delgado-Barrio). Chem Phys 2012. [DOI: 10.1016/j.chemphys.2011.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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13
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Sartakov BG, Toennies JP, Vilesov AF. Infrared spectroscopy of carbonyl sulfide inside a pure3He droplet. J Chem Phys 2012; 136:134316. [DOI: 10.1063/1.3697475] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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Valdés A, Barragán P, Sanz-Sanz C, Prosmiti R, Villarreal P, Delgado-Barrio G. Theoretical simulations of the vibrational predissociation spectra of H 5 + and D 5 + clusters. Theor Chem Acc 2012. [DOI: 10.1007/s00214-012-1210-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Rodríguez-Cantano R, López-Durán D, González-Lezana T, Delgado-Barrio G, Villarreal P, Yurtsever E, Gianturco FA. Spin-polarized Rb2 interacting with bosonic He atoms: potential energy surface and quantum structures of small clusters. J Phys Chem A 2012; 116:2394-404. [PMID: 22320704 DOI: 10.1021/jp3004932] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A new full-dimension potential energy surface of the three-body He-Rb₂(³Σ(u)(+)) complex and a quantum study of small (⁴He)(N)-Rb₂(³Σ(u)(+)) clusters, 1 ≤ N ≤ 4, are presented. We have accurately fitted the ab initio points of the interaction to an analytical form and addressed the dopant's vibration, which is found to be negligible. A Variational approach and a Diffusion Monte Carlo technique have been applied to yield energy and geometric properties of the selected species. Our quantum structure calculations show a transition in the arrangements of the helium atoms from N = 2, where they tend to be separated across the diatomic bond, to N = 4, in which a closer packing of the rare gas particles is reached, guided by the dominance of the He-He potential over the weaker interaction of the latter adatoms with the doping dimer. The deepest well of the He-Rb₂ interaction is placed at the T-shape configuration, a feature which causes the dopant to be located as parallel to the helium "minidroplet". Our results are shown to agree with previous findings on this and on similar systems.
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Valdés A, Prosmiti R, Villarreal P, Delgado-Barrio G. Full-dimensional multi configuration time dependent Hartree calculations of the ground and vibrationally excited states of He2,3Br2 clusters. J Chem Phys 2011; 135:054303. [PMID: 21823696 DOI: 10.1063/1.3618727] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Quantum dynamics calculations are reported for the tetra-, and penta-atomic van der Waals He(N)Br(2) complexes using the multiconfiguration time-dependent Hartree (MCTDH) method. The computations are carried out in satellite coordinates, and the kinetic energy operator in this set of coordinates is given. A scheme for the representation of the potential energy surface based on the sum of the three-body HeBr(2) interactions at CSSD(T) level plus the He-He interaction is employed. The potential surfaces show multiple close lying minima, and a quantum description of such highly floppy multiminima systems is presented. Benchmark, full-dimensional converged results on ground vibrational/zero-point energies are reported and compared with recent experimental data available for all these complexes, as well as with previous variational quantum calculations for the smaller HeBr(2) and He(2)Br(2) complexes on the same surface. Some low-lying vibrationally excited eigenstates are also computed by block improved relaxation calculations. The binding energies and the corresponding vibrationally averaged structures are determined for different conformers of these complexes. Their relative stability is discussed, and contributes to evaluate the importance of the multiple-minima topology of the underlying potential surface.
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Affiliation(s)
- Alvaro Valdés
- Instituto de Física Fundamental (IFF-CSIC), CSIC, Madrid, Spain.
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Pérez de Tudela R, López-Durán D, González-Lezana T, Delgado-Barrio G, Villarreal P, Gianturco FA, Yurtsever E. Quantum features of a barely bound molecular dopant: Cs2(3Σu) in bosonic helium droplets of variable size. J Phys Chem A 2011; 115:6892-902. [PMID: 21585200 DOI: 10.1021/jp111825n] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present in this work the study of small (4)He(N)-Cs(2)((3)Σ(u)) aggregates (2 ≤ N ≤ 30) through combined variational, diffusion Monte Carlo (DMC), and path integral Monte Carlo (PIMC) calculations. The full surface is modeled as an addition of He-Cs(2) interactions and He-He potentials. Given the negligible strength and large range of the He-Cs(2) interaction as compared with the one for He-He, a propensity of the helium atoms to pack themselves together, leaving outside the molecular dopant is to be expected. DMC calculations determine the onset of helium gathering at N = 3. To analyze energetic and structural properties as a function of N, PIMC calculations with no bosonic exchange, i.e., Boltzmann statistics, at low temperatures are carried out. At T = 0.1 K, although acceptable one-particle He-Cs(2) distributions are obtained, two-particle He-He distributions are not well described, indicating that the proper symmetry should be taken into account. PIMC distributions at T = 1 K already compare well with DMC ones and show minor exchange effects, although binding energies are still far from having converged in terms of the number of quantum beads. As N increases, the He-He PIMC pair correlation function shows a clear tendency to coincide with the experimental boson-liquid helium one at that temperature. It supports the picture of a helium droplet which carries the molecular impurity on its surface, as found earlier for other triplet dimers.
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de Lara-Castells MP, Aguirre NF, Villarreal P, Barrio GD, Mitrushchenkov AO. Quantum solvent states and rovibrational spectra of small doped H3e clusters through the full-configuration-interaction nuclear orbital approach: The (H3e)N–Cl2(X) case (N≤4). J Chem Phys 2010; 132:194313. [DOI: 10.1063/1.3425997] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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DFT Calculations of Vibrational Frequencies of Carbon–Nitrogen Clusters: Raman Spectra of Carbon Nitrides. J CLUST SCI 2010. [DOI: 10.1007/s10876-010-0299-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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21
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Prosmiti R, Delgado-Barrio G, Villarreal P, Yurtsever E, Coccia E, Gianturco FA. Structuring a Quantum Solvent around a Weakly Bound Dopant: The He−Cs2(3Σu) Complex. J Phys Chem A 2009; 113:14718-29. [DOI: 10.1021/jp9048583] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | - Ersin Yurtsever
- Department of Chemistry, Koç University, Rumeligeneri Yolu, 34450 Sariyer, Istanbul, Turkey
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22
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Guardiola R, Navarro J, Mateo D, Barranco M. Ca impurity in small mixed (4)He-(3)He clusters. J Chem Phys 2009; 131:174110. [PMID: 19895001 DOI: 10.1063/1.3258273] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The structure of small mixed helium clusters doped with one calcium atom has been determined within the diffusion Monte Carlo framework. The results show that the calcium atom sits at the (4)He-(3)He interface. This is in agreement with previous studies, both experimental and theoretical, performed for large clusters. A comparison between the results obtained for the largest cluster we have considered for each isotope shows a clear tendency of the Ca atom to reside in a deep dimple at the surface of the cluster for (4)He clusters, and to become fully solvated for (3)He clusters. We have calculated the absorption spectrum of Ca around the 4s4p<--4s(2) transition and have found that it is blueshifted from that of the free-atom transition by an amount that depends on the size and composition of the cluster.
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Affiliation(s)
- R Guardiola
- IFIC (CSIC-Universidad de Valencia), Apartado Postal 22085, E-46.071 Valencia, Spain
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de Lara-Castells MP, Villarreal P, Delgado-Barrio G, Mitrushchenkov AO. An optimized full-configuration-interaction nuclear orbital approach to a “hard-core” interaction problem: Application to ([sup 3]He)[sub N]–Cl[sub 2](B) clusters (N≤4). J Chem Phys 2009; 131:194101. [DOI: 10.1063/1.3263016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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González-Martínez M, Arbelo-González W, Rubayo-Soneira J, Bonnet L, Rayez JC. Vibrational predissociation of van der Waals complexes: Quasi-classical results with Gaussian-weighted trajectories. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.08.052] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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25
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Roncero O, de Lara-Castells MP, Delgado-Barrio G, Villarreal P, Stoecklin T, Voronin A, Rayez JC. Exact, Born-Oppenheimer, and quantum-chemistry-like calculations in helium clusters doped with light molecules: The He2N2(X) system. J Chem Phys 2008; 128:164313. [PMID: 18447445 DOI: 10.1063/1.2900560] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Helium clusters doped with diatomic molecules, He(N)-BC, have been recently studied by means of a quantum-chemistry-like approach. The model treats He atoms as "electrons" and dopants as "nuclei" in standard electronic structure calculations. Due to the large mass difference between He atoms and electrons, and to the replacement of Coulomb interactions by intermolecular potentials, it is worth assessing up to what extent are the approximations involved in this model, i.e., decoupling of the BC rotation from the He-atom orbital angular momenta and Born-Oppenheimer separation of the BC stretch versus the He motions, accurate enough. These issues have been previously tackled elsewhere for the (4)He(2)-Br(2)(X) system, which contains a heavy dopant [Roncero et al., Int. J. Quantum Chem. 107, 2756 (2007)]. Here, we consider a similar cluster but with a much lighter dopant such as N(2)(X). Although the model does not provide the correct energy levels for the cluster, positions and intensities of the main detectable lines of the vibrotational Raman spectrum at low temperature are accurately reproduced.
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Affiliation(s)
- O Roncero
- Instituto de Física Fundamental (C.S.I.C.), Serrano 123, E-28006 Madrid, Spain
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de Lara-Castells MP, Delgado-Barrio G, Villarreal P, Mitrushchenkov AO. A full-configuration interaction “nuclear orbital” method to study doped HeN3 clusters (N⩽4). J Chem Phys 2006; 125:221101. [PMID: 17176126 DOI: 10.1063/1.2403846] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
An efficient full configuration interaction (FCI) treatment, based on the Jacobi-Davidson algorithm, is developed in order to study small doped (3)He(N) clusters. The state of each He atom in a given cluster is described by a set of wave-functions which by extention of the quantum-chemistry notation are caller here "nuclear orbitals". The FCI treatment is applied to the calculation of binding energies and helium natural orbitals of (3)He(N)...Br(2)(X) complexes. In agreement with our previous calculations using a Hartree-Fock approach [Phys. Rev. Lett. 93, 053401 (2004)], in which the He-He interaction is modified at small distances to account for short-range correlation effects, the lowest-energy states of each multiplet are found to be very close in energy. The natural orbital analysis, in turn, indicates the adequacy of the "nuclear orbital" approach in these systems.
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Affiliation(s)
- M P de Lara-Castells
- Instituto de Matemáticas y Física Fundamental (C.S.I.C.), Serrano 123, E-28006 Madrid, Spain.
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Felker PM. Solvent configuration-interaction calculations of intermolecular states in molecule-(atom)N clusters: application to Br2-4HeN. J Chem Phys 2006; 125:184313. [PMID: 17115758 DOI: 10.1063/1.2371032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We describe variational calculations of J=0 intermolecular states in Br(2)-(4)He(N) clusters. The method employed is analogous to configuration-interaction calculations in electronic-structure work and relies on the ability to express the intermolecular Hamiltonian H(v) as a sum of one- and two-body terms. A basis set is built up from solutions to the Schrödinger equation in which only the one-body terms of H(v) are included. These configurations are products of N=1 eigenstates. The matrix of H(v) in a symmetry-adapted configuration basis is then computed, the two-body terms of H(v) serving to couple different configurations. This computation involves integrals of dimension five or less. Filter diagonalization is then used to obtain energies and eigenfunctions within a selected energy range. Results on clusters having N=2-5 are reported.
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Affiliation(s)
- Peter M Felker
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
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Bodo E, Lara M, Gianturco FA. Isotopic replacement in ionic systems: The He2+4+He3→He3He+4+He4 reaction. J Chem Phys 2006; 124:044308. [PMID: 16460163 DOI: 10.1063/1.2155480] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Full quantum dynamics calculations have been carried out for the ionic reaction (4)He(2) (+)+(3)He and state-to-state reactive probabilities have been obtained using both time-dependent and time-independent approaches. An accurate ab initio potential-energy surface has been employed for the present quantum dynamics and the two sets of results are shown to be in agreement with each other. The results for zero total angular momentum suggest a marked presence of atom exchange (isotopic replacement) reaction with probabilities as high as 60%. The reaction probabilities are only weakly dependent on the initial vibrational state of the reactants, while they are slightly more sensitive to the degree of rotational excitation. A brief discussion of the results for selected higher total angular momentum values is also presented, while the l-shifting approximation [S. K. Gray et al., Phys. Chem. Chem. Phys. 1, 1141 (1999)] has been used to provide estimates of the total reaction rates for the title process. Such rates are found to be large enough to possibly become experimentally accessible.
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Affiliation(s)
- Enrico Bodo
- Department of Chemistry, University of Rome La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy
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Di Paola C, Gianturco FA, López-Durán D, de Lara-Castells MP, Delgado-Barrio G, Villarreal P, Jellinek J. Br2(X) Microsolvation in Helium Clusters: Effect of the Interaction on the Quantum Solvent Density Distribution. Chemphyschem 2005; 6:1348-56. [PMID: 15968696 DOI: 10.1002/cphc.200400530] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The Born-Oppenheimer potential energy surface for the Br2(X) molecule interacting with a varying number of 4He bosons is constructed following two different schemes which employ either a full ab initio evaluation of the Br2-He interaction forces or an estimate of the latter through an empirical model. Both descriptions are employed by carrying out diffusion Monte Carlo (DMC) calculations of the ground-state energies and quantum wavefunctions for Br2-(He)n clusters with n up to 24. The results clearly indicate, for both interactions, the occurrence of the full solvation of the molecular dopant within the quantum bosonic "solvent" but also show differences between the two models in terms of the expected density distributions of the surrounding particles within the shorter-range region that makes up the clusters with smaller n values. Our calculations also show that such differences become insignificant for the larger 4He clusters surrounding the Br2 molecule, where density profiles and bulk behaviour are chiefly driven by the solvent structure, once n values reach the region of 15-20 adatoms.
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Affiliation(s)
- Cono Di Paola
- Department of Chemistry and INFM, University of Rome, La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy
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