Nuclear quantum effects on the dynamics and glass behavior of a monatomic liquid with two liquid states

Eltareb, Ali; López, Gustavo E.; Giovambattista, Nicolás

doi:10.1063/5.0087680

Cited by 6 publications

(3 citation statements)

References 65 publications

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“…63 The R g of the O and H atoms of water in ice I h and during the cooling-induced liquid-to-LDA transformation (P = 0.1 MPa) are shown in Figure 6b. Consistent with previous computational studies performed on water-like models, 32 R g (T) increases as the temperature is decreased (i.e., the O and H atoms become increasingly delocalized upon cooling at lower temperatures). The delocalization of the H atoms in ice I h and LDA is considerable.…”

Section: Resultssupporting

confidence: 89%

“…For example, NQE are responsible for the difference in the melting temperature of H 2 O and D 2 O (δ T ≈ 4 K) as well as in the corresponding temperature of maximum density (δ T ≈ 7 K) and the glass transition temperature (δ T ≈ 10 K) . In addition, computer simulations of water-like models, show that the inclusion of NQE can have a significant impact on the thermodynamic, dynamical, and structural properties of the low-temperature liquid as well as the glass state. − At present, the role of NQE on LDA and HDA remains poorly understood.…”

Section: Introductionmentioning

confidence: 99%

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The Importance of Nuclear Quantum Effects on the Thermodynamic and Structural Properties of Low-Density Amorphous Ice: A Comparison with Hexagonal Ice

2023

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We study the nuclear quantum effects (NQE) on the thermodynamic properties of low-density amorphous ice (LDA) and hexagonal ice (I h ) at P = 0.1 MPa and T ≥ 25 K. Our results are based on path-integral molecular dynamics (PIMD) and classical MD simulations of H 2 O and D 2 O using the q-TIP4P/F water model. We show that the inclusion of NQE is necessary to reproduce the experimental properties of LDA and ice I h . While MD simulations (no NQE) predict that the density ρ(T) of LDA and ice I h increases monotonically upon cooling, PIMD simulations indicate the presence of a density maximum in LDA and ice I h . MD and PIMD simulations also predict a qualitatively different Tdependence for the thermal expansion coefficient α P (T) and bulk modulus B(T) of both LDA and ice I h . Remarkably, the ρ(T), α P (T), and B(T) of LDA are practically identical to those of ice I h . The origin of the observed NQE is due to the delocalization of the H atoms, which is identical in LDA and ice I h . H atoms delocalize considerably (over a distance ≈ 20−25% of the OH covalent-bond length) and anisotropically (preferentially perpendicular to the OH covalent bond), leading to less linear hydrogen bonds HB (larger HOO angles and longer OO separations) than observed in classical MD simulations.

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Section: Resultssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

The Importance of Nuclear Quantum Effects on the Thermodynamic and Structural Properties of Low-Density Amorphous Ice: A Comparison with Hexagonal Ice

2023

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“…In order to understand the role of quantum mechanics in the PEL formalism, we follow refs and − and perform PIMC simulations of the FJ liquid using different values of the Planck’s constant h . This allows us to simulate the same liquid in the classical limit ( h = 0) as well as in the quantum regime ( h > 0).…”

Section: Methodsmentioning

confidence: 99%

The Harmonic and Gaussian Approximations in the Potential Energy Landscape Formalism for Quantum Liquids

Zhou,

Lopez,

Giovambattista

2024

J. Chem. Theory Comput.

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The potential energy landscape (PEL) formalism has been used in the past to describe the behavior of classical low-temperature liquids and glasses. Here, we extend the PEL formalism to describe the behavior of liquids and glasses that obey quantum mechanics. In particular, we focus on the (i) harmonic and (ii) Gaussian approximations of the PEL, which have been commonly used to describe classical systems, and show how these approximations can be applied to quantum liquids/glasses. Contrary to the case of classical liquids/glasses, the PEL of quantum liquids is temperature-dependent, and hence, the main expressions resulting from approximations (i) and (ii) depend on the nature (classical vs quantum) of the system. The resulting theoretical expressions from the PEL formalism are compared with results from path-integral Monte Carlo (PIMC) simulations of a monatomic model liquid. In the PIMC simulations, every atom of the quantum liquid is represented by a ring-polymer. Our PIMC simulations show that at the local minima of the PEL (inherent structures, or IS), sampled over a wide range of temperatures and volumes, the ring-polymers are collapsed. This considerably facilitates the description of quantum liquids using the PEL formalism. Specifically, the normal modes of the ring-polymer system/quantum liquid at an IS can be calculated analytically if the normal modes of the classical liquid counterpart are known (as obtained, e.g., from classical MC or molecular dynamics simulations of the corresponding atomic liquid).

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Potential energy landscape formalism for quantum molecular liquids

Eltareb,

Zhou,

Lopez

et al. 2024

Commun Chem

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The potential energy landscape (PEL) formalism is a powerful tool within statistical mechanics to study the thermodynamic properties of classical low-temperature liquids and glasses. Recently, the PEL formalism has been extended to liquids/glasses that obey quantum mechanics, but applications have been limited to atomistic model liquids. In this work, we extend the PEL formalism to liquid/glassy water using path-integral molecular dynamics (PIMD) simulations, where nuclear quantum effects (NQE) are included. Our PIMD simulations, based on the q-TIP4P/F water model, show that the PEL of quantum water is both Gaussian and anharmonic. Importantly, the ring-polymers associated to the O/H atoms in the PIMD simulations, collapse at the local minima of the PEL (inherent structures, IS) for both liquid and glassy states. This allows us to calculate, analytically, the IS vibrational density of states (IS-VDOS) of the ring-polymer system using the IS-VDOS of classical water (obtained from classical MD simulations). The role of NQE on the structural properties of liquid/glassy water at various pressures are discussed in detail. Overall, our results demonstrate that the PEL formalism can effectively describe the behavior of molecular liquids at low temperatures and in the glass states, regardless of whether the liquid/glass obeys classical or quantum mechanics.

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Nuclear quantum effects on the dynamics and glass behavior of a monatomic liquid with two liquid states

Cited by 6 publications

References 65 publications

The Importance of Nuclear Quantum Effects on the Thermodynamic and Structural Properties of Low-Density Amorphous Ice: A Comparison with Hexagonal Ice

The Importance of Nuclear Quantum Effects on the Thermodynamic and Structural Properties of Low-Density Amorphous Ice: A Comparison with Hexagonal Ice

The Harmonic and Gaussian Approximations in the Potential Energy Landscape Formalism for Quantum Liquids

Potential energy landscape formalism for quantum molecular liquids

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