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Curotto E. Ion-Stockmayer clusters: Minima, classical thermodynamics, and variational ground state estimates of Li+(CH3NO2)n(n= 1–20). J Chem Phys 2015; 143:214301. [DOI: 10.1063/1.4936587] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- 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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Curotto E, Mella M. On the convergence of diffusion Monte Carlo in non-Euclidean spaces. II. Diffusion with sources and sinks. J Chem Phys 2015; 142:114111. [PMID: 25796235 DOI: 10.1063/1.4914516] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We test the second order Milstein method adapted to simulate diffusion in general compact Riemann manifolds on a number of systems characterized by nonconfining potential energy surfaces of increasing complexity. For the 2-sphere and more complex spaces derived from it, we compare the Milstein method with a number of other first and second order approaches. In each case tested, we find evidence that demonstrate the versatility and relative ease of implementation of the Milstein method derived in Part I.
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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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Wolf S, Curotto E. Ring polymer dynamics for rigid tops with an improved integrator. J Chem Phys 2014; 141:024116. [DOI: 10.1063/1.4887460] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Mielke SL, Dinpajooh M, Siepmann JI, Truhlar DG. Efficient methods for including quantum effects in Monte Carlo calculations of large systems: Extension of the displaced points path integral method and other effective potential methods to calculate properties and distributions. J Chem Phys 2013; 138:014110. [PMID: 23298031 DOI: 10.1063/1.4772667] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Steven L Mielke
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, USA.
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Abstract
We formulate an extension of the ring polymer dynamics approach to curved spaces using stereographic projection coordinates. We test the theory by simulating the particle in a ring, T(1), mapped by a stereographic projection using three potentials. Two of these are quadratic, and one is a nonconfining sinusoidal model. We propose a new class of algorithms for the integration of the ring polymer Hamilton equations in curved spaces. These are designed to improve the energy conservation of symplectic integrators based on the split operator approach. For manifolds, the position-position autocorrelation function can be formulated in numerous ways. We find that the position-position autocorrelation function computed from configurations in the Euclidean space R(2) that contains T(1) as a submanifold has the best statistical properties. The agreement with exact results obtained with vector space methods is excellent for all three potentials, for all values of time in the interval simulated, and for a relatively broad range of temperatures.
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Affiliation(s)
- S Wolf
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
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Curotto E, Mella M. Quantum Monte Carlo simulations of selected ammonia clusters (n = 2–5): Isotope effects on the ground state of typical hydrogen bonded systems. J Chem Phys 2010; 133:214301. [DOI: 10.1063/1.3506027] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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Asare E, Musah AR, Curotto E, Freeman DL, Doll JD. The thermodynamic and ground state properties of the TIP4P water octamer. J Chem Phys 2009; 131:184508. [DOI: 10.1063/1.3259047] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Lubombo C, Curotto E, Janeiro Barral PE, Mella M. Thermodynamic properties of ammonia clusters (NH3)n n=2–11: Comparing classical and quantum simulation results for hydrogen bonded species. J Chem Phys 2009; 131:034312. [DOI: 10.1063/1.3159398] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Mielke SL, Truhlar DG. Improved Methods for Feynman Path Integral Calculations of Vibrational−Rotational Free Energies and Application to Isotopic Fractionation of Hydrated Chloride Ions. J Phys Chem A 2009; 113:4817-27. [DOI: 10.1021/jp900834u] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Steven L. Mielke
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431
| | - Donald G. Truhlar
- Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431
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Curotto E, Freeman DL, Doll JD. A stereographic projection path integral study of the coupling between the orientation and the bending degrees of freedom of water. J Chem Phys 2008; 128:204107. [DOI: 10.1063/1.2925681] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Luan T, Curotto E, Mella M. Importance sampling for quantum Monte Carlo in manifolds: Addressing the time scale problem in simulations of molecular aggregates. J Chem Phys 2008; 128:164102. [DOI: 10.1063/1.2898539] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Avilés MW, McCandless ML, Curotto E. Stereographic projection path integral simulations of (HCl)n clusters (n=2–5): Evidence of quantum induced melting in small hydrogen bonded networks. J Chem Phys 2008; 128:124517. [DOI: 10.1063/1.2837802] [Citation(s) in RCA: 16] [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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Avilés MW, Curotto E. Stereographic projection diffusion monte carlo (SPDMC) algorithms for molecular condensed matter. J Phys Chem A 2007; 111:2610-8. [PMID: 17388350 DOI: 10.1021/jp066827i] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We develop and test three algorithms for diffusion Monte Carlo simulations in non-Euclidean manifolds. The methods are based on the construction of the "velocity" distribution by rejection techniques and are capable of functioning in a broad class of non-Euclidean spaces generated by holonomic constraints. The formulation of the propagator for non-Euclidean manifolds avoids the use of Lagrange multipliers; it is derived instead from the Feynman quantization in manifolds proposed by DeWitt. The manifolds are mapped onto Rd by using stereographic projection coordinates. Numerical tests are conducted for the particle in a ring of unit radius subjected to a sinusoidal potential, for the electron in the field of an infinitely massive proton, and for a water molecule modeled as an asymmetric top subjected to an external field.
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Affiliation(s)
- Michael W Avilés
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
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Langley SF, Curotto E, Freeman DL, Doll JD. Rigid quantum Monte Carlo simulations of condensed molecular matter: Water clusters in the n=2→8 range. J Chem Phys 2007; 126:084506. [PMID: 17343457 DOI: 10.1063/1.2484229] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The numerical advantage of quantum Monte Carlo simulations of rigid bodies relative to the flexible simulations is investigated for some simple systems. The results show that if high frequency modes in molecular condensed matter are predominantly in the ground state, the convergence of path integral simulations becomes nonuniform. Rigid body quantum parallel tempering simulations are necessary to accurately capture thermodynamic phenomena in the temperature range where the dynamics are influenced by intermolecular degrees of freedom; the stereographic projection path integral adapted for quantum simulations of asymmetric tops is a significantly more efficient strategy compared with Cartesian coordinate simulations for molecular condensed matter under these conditions. The reweighted random series approach for stereographic path integral Monte Carlo is refined and implemented for the quantum simulation of water clusters treated as an assembly of rigid asymmetric tops.
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Affiliation(s)
- Stephen F Langley
- Department of Chemistry, Arcadia University, Glenside, Pennsylvania 19038-3295, USA
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Avilés MW, Gray PT, Curotto E. Stereographic projection path-integral simulations of (HF)n clusters. J Chem Phys 2006; 124:174305. [PMID: 16689569 DOI: 10.1063/1.2192773] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We perform several quantum canonical ensemble simulations of (HF)(n) clusters. The HF stretches are rigid, and the stereographic projection path-integral method is employed for the simulation in the resulting curved configuration space. We make use of the reweighted random series techniques to accelerate the convergence of the path-integral simulation with respect to the number of path coefficients. We develop and test estimators for the total energy and heat capacity based on a finite difference approach for non-Euclidean spaces. The quantum effects at temperatures below 400 K are substantial for all sizes. We observe interesting thermodynamic behaviors in the quantum simulations of the octamer and the heptamer.
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Affiliation(s)
- Michael W Avilés
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038, USA
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Curotto E. A reweighted random series method for stereographic projection path integrals. J Chem Phys 2005; 123:134102. [PMID: 16223270 DOI: 10.1063/1.2036970] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
A set of general reweighted random series methods for metric affine spaces is developed. The extension of the theorems to metric affine spaces demands the introduction of a configuration-independent reference metric tensor; this geometric object is used to treat the path expansion coefficients beyond the core path, in both the partial averaging and the reweighted random series approach. Numerical tests are conducted by simulating a particle in a ring. The reweighted random series results show better convergence properties and better statistical quality at a fraction of the cost compared with the related partial averaging simulation.
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Affiliation(s)
- E Curotto
- Department of Chemistry and Physics, Arcadia University, Glenside, Pennsylvania 19038, USA.
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