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Zane AR, Curotto E. Electrolyte clusters as hydrogen sponges: diffusion Monte Carlo simulations. Phys Chem Chem Phys 2022; 24:26094-26101. [PMID: 36268906 DOI: 10.1039/d2cp03658d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
We carry out Diffusion Monte Carlo simulations of up to five hydrogen molecules aggregated with two Stockmayer clusters that solvate a single lithium ion. The first one contains six point dipole solvent particles with parameters tuned to emulate nitromethane. The second cluster is a relative large system investigated recently [G. DiEmma, S. Kalette, and E. Curotto, Chem. Phys. Lett. 2019, 725, 80-86]. In both cases we find that the aggregated hydrogen molecules perturb significantly the ground state of the host cluster and form a distorted tetrahedral cage around the Li+ ion. The fifth hydrogen molecule is absorbed by the larger Stockmayer cluster while remaining in the proximity of the solvated charge.
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Affiliation(s)
- A R Zane
- Department of Chemistry & Physics Arcadia University, 450 S. Easton Rd., Glenside, PA 19038, USA.
| | - E Curotto
- Department of Chemistry & Physics Arcadia University, 450 S. Easton Rd., Glenside, PA 19038, USA.
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Stringer A, Curotto E. An ergodic measure for Diffusion Monte Carlo ground state wavefunctions: Application to a hydrogen cluster with an isotopic impurity. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.136728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Curotto E, Mella M. Diffusion Monte Carlo simulations of gas phase and adsorbed D 2-(H 2) n clusters. J Chem Phys 2018; 148:102315. [PMID: 29544319 DOI: 10.1063/1.5000372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have computed ground state energies and analyzed radial distributions for several gas phase and adsorbed D2(H2)n and HD(H2)n clusters. An external model potential designed to mimic ionic adsorption sites inside porous materials is used [M. Mella and E. Curotto, J. Phys. Chem. A 121, 5005 (2017)]. The isotopic substitution lowers the ground state energies by the expected amount based on the mass differences when these are compared with the energies of the pure clusters in the gas phase. A similar impact is found for adsorbed aggregates. The dissociation energy of D2 from the adsorbed clusters is always much higher than that of H2 from both pure and doped aggregates. Radial distributions of D2 and H2 are compared for both the gas phase and adsorbed species. For the gas phase clusters, two types of hydrogen-hydrogen interactions are considered: one based on the assumption that rotations and translations are adiabatically decoupled and the other based on nonisotropic four-dimensional potential. In the gas phase clusters of sufficiently large size, we find the heavier isotopomer more likely to be near the center of mass. However, there is a considerable overlap among the radial distributions of the two species. For the adsorbed clusters, we invariably find the heavy isotope located closer to the attractive interaction source than H2, and at the periphery of the aggregate, H2 molecules being substantially excluded from the interaction with the source. This finding rationalizes the dissociation energy results. For D2-(H2)n clusters with n≥12, such preference leads to the desorption of D2 from the aggregate, a phenomenon driven by the minimization of the total energy that can be obtained by reducing the confinement of (H2)12. The same happens for (H2)13, indicating that such an effect may be quite general and impact on the absorption of quantum species inside porous materials.
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Affiliation(s)
- E Curotto
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
| | - M Mella
- Dipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell'Insubria, Via Valleggio 11, 22100 Como, Italy
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Mella M, Curotto E. Assessment of the Effects of Anisotropic Interactions among Hydrogen Molecules and Their Isotopologues: A Diffusion Monte Carlo Investigation of Gas Phase and Adsorbed Clusters. J Phys Chem A 2017; 121:5005-5017. [DOI: 10.1021/acs.jpca.7b03768] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Massimo Mella
- Dipartimento
di Scienza ed Alta Tecnologia, Università degli Studi dell’Insubria, via Valleggio 11, 22100 Como, Italy
| | - E. Curotto
- Department
of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, United States
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Ramírez-Garza OA, Méndez-Alcaraz JM, González-Mozuelos P. Structural and dynamic inhomogeneities induced by curvature gradients in elliptic colloidal halos of paramagnetic particles. J Chem Phys 2017; 146:194903. [PMID: 28527452 DOI: 10.1063/1.4983496] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Paramagnetic colloidal particles distributed along an ellipse are used as a model system to study the effects of curvature gradients on the structure and dynamics of colloids in curved manifolds. Unlike what happens for circular and spherical systems, in the present case, the equilibrium one-particle distribution function displays inhomogeneities due to the changing curvature along the ellipse. The ensuing effects on the two-body correlations are also analyzed, leading to the observation of anisotropic and long-ranged effects. Another noticeable consequence is the slowing down of the self-diffusion of these particles, which for large eccentricities may induce metastable states; this is evaluated by means of the time-dependent self-distribution.
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Affiliation(s)
- O A Ramírez-Garza
- Departamento de Física, Cinvestav del I. P. N., Ave. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, Ciudad de México, C.P. 07360, Mexico
| | - J M Méndez-Alcaraz
- Departamento de Física, Cinvestav del I. P. N., Ave. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, Ciudad de México, C.P. 07360, Mexico
| | - P González-Mozuelos
- Departamento de Física, Cinvestav del I. P. N., Ave. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, Ciudad de México, C.P. 07360, Mexico
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Mella M, Curotto E. Quest for Inexpensive Hydrogen Isotopic Fractionation: Do We Need 2D Quantum Confining in Porous Materials or Are Rough Surfaces Enough? The Case of Ammonia Nanoclusters. J Phys Chem A 2016; 120:8148-8159. [PMID: 27704841 DOI: 10.1021/acs.jpca.6b08005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We study the adsorption energetics and quantum properties of the molecular hydrogen isotopes H2, D2, and T2 onto the surface of rigid ammonia nanoclusters with quantum simulations and accurate model potential energy surfaces (PES). A highly efficient diffusion Monte Carlo (DMC) algorithm for rigid rotors allowed us to accurately define zero-point adsorption energies for the three isotopes, as well as the degree of translational and rotational delocalization that each affords on the surface. From the data emerges that the quantum adsorption energy (Eads) of T2 can be up to twice the one of H2 at 0 K, suggesting the possibility of exploiting some form of solid ammonia to selectivity separate hydrogen isotopes at low temperatures (≃20 K). This is discussed by focusing on the structural motif that may be more effective for the task. The analysis of the contributions to Eads, however, surprisingly indicates that the average kinetic energy (Ekin) and rotation energy (Erotkin) of T2 can also be, respectively, 2 times and 20 times higher than those of H2; this finding markedly deviates from what is predicted for hydrogen molecules inside carbon nanotubes (CNT) or metallic-organic frameworks (MOF), where Ekin and Erotkin is higher for H2 due to the unavoidable effects of confinement and hindrance to its rotational motion. The rationale for these differences is provided by the geometrical distributions for the rigid rotors, which reveal an increasingly stronger coupling between rotational and translational degrees of freedom upon increasing the isotopic mass. This effect has never been observed before on adsorbing surfaces (e.g., graphite) and is induced by a strongly anisotropic and anharmonic bowl-like potential experienced by the rotors.
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Affiliation(s)
- Massimo Mella
- Dipartimento di Scienza ed Alta Tecnologia, Università degli Studi dell'Insubria , via Valleggio 9, 22100 Como, Italy
| | - E Curotto
- Department of Chemistry and Physics, Arcadia University , Glenside, Pennsylvania 19038-3295, United States
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Christensen HM, Jake LC, Curotto E. Smart darting diffusion Monte Carlo: Applications to lithium ion-Stockmayer clusters. J Chem Phys 2016; 144:174115. [PMID: 27155633 DOI: 10.1063/1.4948562] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In a recent investigation [K. Roberts et al., J. Chem. Phys. 136, 074104 (2012)], we have shown that, for a sufficiently complex potential, the Diffusion Monte Carlo (DMC) random walk can become quasiergodic, and we have introduced smart darting-like moves to improve the sampling. In this article, we systematically characterize the bias that smart darting moves introduce in the estimate of the ground state energy of a bosonic system. We then test a simple approach to eliminate completely such bias from the results. The approach is applied for the determination of the ground state of lithium ion-n-dipoles clusters in the n = 8-20 range. For these, the smart darting diffusion Monte Carlo simulations find the same ground state energy and mixed-distribution as the traditional approach for n < 14. In larger systems we find that while the ground state energies agree quantitatively with or without smart darting moves, the mixed-distributions can be significantly different. Some evidence is offered to conclude that introducing smart darting-like moves in traditional DMC simulations may produce a more reliable ground state mixed-distribution.
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Affiliation(s)
- H M Christensen
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
| | - L C Jake
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
| | - E Curotto
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
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Curotto E, Mella M. On the convergence of diffusion Monte Carlo in non-Euclidean spaces. I. Free diffusion. J Chem Phys 2015; 142:114110. [PMID: 25796234 DOI: 10.1063/1.4914515] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We develop a set of diffusion Monte Carlo algorithms for general compactly supported Riemannian manifolds that converge weakly to second order with respect to the time step. The approaches are designed to work for cases that include non-orthogonal coordinate systems, nonuniform metric tensors, manifold boundaries, and multiply connected spaces. The methods do not require specially designed coordinate charts and can in principle work with atlases of charts. Several numerical tests for free diffusion in compactly supported Riemannian manifolds are carried out for spaces relevant to the chemical physics community. These include the circle, the 2-sphere, and the ellipsoid of inertia mapped with traditional angles. In all cases, we observe second order convergence, and in the case of the sphere, we gain insight into the function of the advection term that is generated by the curved nature of the space.
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Affiliation(s)
- E Curotto
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
| | - Massimo Mella
- Dipartimento di Scienza ed Alta Tecnologia, via Valleggio 9, Università degli studi dell'Insubria, 22100 Como, Italy
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