Path integral ground state study of finite-size systems: Application to small (parahydrogen)N (N=2–20) clusters

Cuervo, Javier; Roy, Pierre‐Nicholas

doi:10.1063/1.2352735

Cited by 75 publications

(91 citation statements)

References 34 publications

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“…Over the past two decades, an intense theoretical and experimental effort has been devoted to the investigation of low T properties of molecular hydrogen. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Evidence of SF has been found in p-H 2 clusters of 15 molecules, doped with a single molecular impurity and embedded in helium nanodroplets. 5 In these experiments, the rotational spectrum of the dopant molecule shows evidence of decoupling from the surrounding medium, below T =0.19 K. This is in turn interpreted as evidence of superfluidity of the medium itself, i.e., the p-H 2 cluster.…”

Section: Introductionmentioning

confidence: 99%

On the Possible “Supersolid” Character of Parahydrogen Clusters

Mezzacapo

2011

J. Phys. Chem. A

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We present results of a theoretical study of structural and superfluid properties of parahydrogen (p-H 2 ) clusters comprising 25, 26 and 27 molecules at low temperature. The microscopic model utilized here is based on the Silvera-Goldman pair potential. Numerical results are obtained by means of Quantum Monte Carlo simulations, making use of the continuousspace Worm Algorithm. The clusters are superfluid in the low temperature limit, but display markedly different physical behaviours. For N=25 and 27, superfluidity at low temperature arises as clusters melt, i.e., become progressively liquid-like as a result of quantum effects. On the other hand, for N = 26 the cluster remains rigid and solid-like. We argue that the cluster (p-H 2 ) 26 can be regarded as a mesoscopic "supersolid". This physical picture is supported by results of simulations in which a single p-H 2 molecule in the cluster is isotopically substituted.

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Section: Introductionmentioning

confidence: 99%

On the Possible “Supersolid” Character of Parahydrogen Clusters

Mezzacapo

2011

J. Phys. Chem. A

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“…The structure and energy of small H 2 clusters in the limit of zero temperature have been studied accurately with both the DMC (Guardiola and Navarro, 2008) and PIGS (Cuervo and Roy, 2006) methods. The presence of magic-cluster sizes, identified with a kink in the chemical potential, have been reported in those studies.…”

Section: Clustersmentioning

confidence: 99%

Simulation and understanding of atomic and molecular quantum crystals

2017

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Quantum crystals abound in the whole range of solid-state species. Below a certain threshold temperature the physical behavior of rare gases ( 4 He and Ne), molecular solids (H 2 and CH 4 ), and some ionic (LiH), covalent (graphite), and metallic (Li) crystals can be only explained in terms of quantum nuclear effects (QNE). A detailed comprehension of the nature of quantum solids is critical for achieving progress in a number of fundamental and applied scientific fields like, for instance, planetary sciences, hydrogen storage, nuclear energy, quantum computing, and nanoelectronics. This review describes the current physical understanding of quantum crystals formed by atoms and small molecules, as well as the wide palette of simulation techniques that are used to investigate them. Relevant aspects in these materials such as phase transformations, structural properties, elasticity, crystalline defects and the effects of reduced dimensionality, are discussed thoroughly. An introduction to quantum Monte Carlo techniques, which in the present context are the simulation methods of choice, and other quantum simulation approaches (e. g., path-integral molecular dynamics and quantum thermal baths) is provided. The overarching objective of this article is twofold. First, to clarify in which crystals and physical situations the disregard of QNE may incur in important bias and erroneous interpretations. And second, to promote the study and appreciation of QNE, a topic that traditionally has been treated in the context of condensed matter physics, within the broad and interdisciplinary areas of materials science.

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“…18 In a one-dimensional channel, like the one provided experimentally by narrow carbon nanotubes, it has been predicted a stable liquid phase in the limit of zero temperature. 19 The largest number of theoretical works have been devoted to the study of small clusters, both pure [20][21][22][23][24][25][26][27][28][29] and doped with impurities. [30][31][32] All these simulations show that p-H 2 becomes superfluid below a certain temperature T = 1-2 K and that the superfluid fraction depends on the number of molecules of the cluster.…”

Section: Introductionmentioning

confidence: 99%

Superfluidity of metastable glassy bulkpara-hydrogen at low temperature

2012

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Molecular para-hydrogen (p-H 2 ) has been proposed theoretically as a possible candidate for superfluidity, but the eventual superfluid transition is hindered by its crystallization. In this work, we study a metastable noncrystalline phase of bulk p-H 2 by means of the path integral Monte Carlo method in order to investigate at which temperature this system can support superfluidity. By choosing accurately the initial configuration and using a noncommensurate simulation box, we have been able to frustrate the formation of the crystal in the simulated system and to calculate the temperature dependence of the one-body density matrix and of the superfluid fraction. We observe a transition to a superfluid phase at temperatures around 1 K. The limit of zero temperature is also studied using the diffusion Monte Carlo method. Results for the energy, condensate fraction, and structure of the metastable liquid phase at T = 0 are reported and compared with the ones obtained for the stable solid phase.

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Path integral ground state study of finite-size systems: Application to small (parahydrogen)N (N=2–20) clusters

Cited by 75 publications

References 34 publications

On the Possible “Supersolid” Character of Parahydrogen Clusters

On the Possible “Supersolid” Character of Parahydrogen Clusters

Simulation and understanding of atomic and molecular quantum crystals

Superfluidity of metastable glassy bulkpara-hydrogen at low temperature

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