“On-the-fly” coupled cluster path-integral molecular dynamics: impact of nuclear quantum effects on the protonated water dimer

Spura, Thomas; Elgabarty, Hossam; Kühne, Thomas D.

doi:10.1039/c4cp05192k

Cited by 33 publications

(44 citation statements)

References 69 publications

(76 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, the 2D distributions are nearly the same at low and room temperature. These conclusions are in agreement with previous studies on this system 94,95 . Some calculations performed with deterministic forces obtained from the reference CCSD(T) PES show that thermal effects start to be significant for temperatures greater than T = 900 K. This confirms that NQE are essential to fully understand the microscopic mechanisms involving the proton dynamics in liquid water at ambient conditions.…”

Section: Resultssupporting

confidence: 94%

“…In the case of the Zundel ion, M = 128 quantum replicas are enough to fully recover the quantum kinetic energy at low temperature, whereas only M = 32 beads are required at room temperature, according to Figure 1. We note that these values are consistent with those frequently used in the literature for this system [93][94][95] .…”

Section: Stability With Respect To the Number Of Beads Msupporting

confidence: 91%

See 1 more Smart Citation

Fully Quantum Description of the Zundel Ion: Combining Variational Quantum Monte Carlo with Path Integral Langevin Dynamics

Mouhat

Sorella

Vuilleumier

et al. 2017

J. Chem. Theory Comput.

View full text Add to dashboard Cite

We introduce a novel approach for a fully quantum description of coupled electron-ion systems from first principles. It combines the variational quantum Monte Carlo solution of the electronic part with the path integral formalism for the quantum nuclear dynamics. On the one hand, the path integral molecular dynamics includes nuclear quantum effects by adding a set of fictitious classical particles (beads) aimed at reproducing nuclear quantum fluctuations via a harmonic kinetic term. On the other hand, variational quantum Monte Carlo can provide Born-Oppenheimer potential energy surfaces with a precision comparable to the most-advanced post-Hartree-Fock approaches, and with a favorable scaling with the system size. In order to cope with the intrinsic noise due to the stochastic nature of quantum Monte Carlo methods, we generalize the path integral molecular dynamics using a Langevin thermostat correlated according to the covariance matrix of quantum Monte Carlo nuclear forces. The variational parameters of the quantum Monte Carlo wave function are evolved during the nuclear dynamics, such that the Born-Oppenheimer potential energy surface is unbiased. Statistical errors on the wave function parameters are reduced by resorting to bead grouping average, which we show to be accurate and well-controlled. Our general algorithm relies on a Trotter breakup between the dynamics driven by ionic forces and the one set by the harmonic interbead couplings. The latter is exactly integrated, even in the presence of the Langevin thermostat, thanks to the mapping onto an Ornstein-Uhlenbeck process. This framework turns out to be also very efficient in the case of noiseless (deterministic) ionic forces. The new implementation is validated on the Zundel ion (HO) by direct comparison with standard path integral Langevin dynamics calculations made with a coupled cluster potential energy surface. Nuclear quantum effects are confirmed to be dominant over thermal effects well beyond room temperature, giving the excess proton an increased mobility by quantum tunneling.

show abstract

Section: Resultssupporting

confidence: 94%

Section: Stability With Respect To the Number Of Beads Msupporting

confidence: 91%

Fully Quantum Description of the Zundel Ion: Combining Variational Quantum Monte Carlo with Path Integral Langevin Dynamics

Mouhat

Sorella

Vuilleumier

et al. 2017

J. Chem. Theory Comput.

View full text Add to dashboard Cite

show abstract

“…In addition recent developments in electronic structure theory and ongoing increases in computational power have made simulations using MP2 theory possible for condensed phase water(251) while recent algorithms have also improved its scaling (252). For small gas phase molecules higher-level methods, such as coupled cluster theory, can also be utilized with PIMD simulations (253). In addition recent simulations of liquid water using highly accurate quantum Monte Carlo surfaces suggest that PIMD simulations of this kind might soon become practical (254).…”

Section: Potential Energy Surfacesmentioning

confidence: 99%

Nuclear Quantum Effects in Water and Aqueous Systems: Experiment, Theory, and Current Challenges

et al. 2016

View full text Add to dashboard Cite

Nuclear quantum effects influence the structure and dynamics of hydrogen bonded systems, such as water, which impacts their observed properties with widely varying magnitudes. This review highlights the recent significant developments in the experiment, theory and simulation of nuclear quantum effects in water. Novel experimental techniques, such as deep inelastic neutron scattering, now provide a detailed view of the role of nuclear quantum effects in water's 2 properties. These have been combined with theoretical developments such as the introduction of the competing quantum effects principle that allows the subtle interplay of water's quantum effects and their manifestation in experimental observables to be explained. We discuss how this principle has recently been used to explain the apparent dichotomy in water's isotope effects, which can range from very large to almost nonexistent depending on the property and conditions. We then review the latest major developments in simulation algorithms and theory that have enabled the efficient inclusion of nuclear quantum effects in molecular simulations, permitting their combination with on-the-fly evaluation of the potential energy surface using electronic structure theory. Finally, we identify current challenges and future opportunities in the area.3

show abstract

“…50 shows results from perturbative theory, together with an extensive review of the literature. Recently, effort is being devoted to studying static properties of the protonated water dimer by new methods, employing on-the-fly coupled cluster electronic structure, 51,52 neural network potentials, 53,54 and variational Monte Carlo. 55,56 This paper describes a reduced rovibrational coupling Cartesian dynamics approach for semiclassical calculations that we apply to the vibrational spectrum of the Zundel cation, as a first step towards the study of bigger protonated water clusters.…”

Section: Introductionmentioning

confidence: 99%

Reduced rovibrational coupling Cartesian dynamics for semiclassical calculations: Application to the spectrum of the Zundel cation

Bertaina

Liberto

Ceotto

2019

The Journal of Chemical Physics

View full text Add to dashboard Cite

We study the vibrational spectrum of the protonated water dimer, by means of a divide-and-conquer semiclassical initial value representation of the quantum propagator, as a first step in the study of larger protonated water clusters. We use the potential energy surface from [Huang et al., J. Chem. Phys. 122, 044308 (2005)]. To tackle such an anharmonic and floppy molecule, we employ fully Cartesian dynamics and carefully reduce the coupling to global rotations in the definition of normal modes. We apply the time-averaging filter and obtain clean power spectra relative to suitable reference states, that highlight the spectral peaks corresponding to the fundamental excitations of the system. Our trajectory-based approach allows us for physical interpretation of the very challenging proton transfer modes. We find that it is important, for such a floppy molecule, to selectively avoid to initially excite lower energy modes, in order to obtain cleaner spectra. The estimated vibrational energies display a mean absolute error (MAE) of ∼ 29cm −1 with respect to available Multi-Configuration time-dependent Hartree calculations and MAE ∼ 14cm −1 when compared to the optically active experimental excitations of the Ne-tagged Zundel cation. The reasonable scaling in the number of trajectories for Monte Carlo convergence is promising for applications to higher dimensional protonated cluster systems.The Zundel cation is the most representative member of the family of protonated water clusters, towards which many computational efforts are being devoted, mainly motivated by a flourishing of experimental results, 11-16 and the request for higher accuracy. [17][18][19][20][21] In this respect, this molecule is a prototypical example that has been tackled by various approaches, given the great biological relevance of the charge transport mechanism in aqueous solutions. [22][23][24][25][26][27] On the experimental side, the vibrational spectrum of the Zundel cation has been investigated by infrared multiphoton photodissociation spectroscopy 28,29 and noble gases predissociation spectroscopy, in particular Argon and Neon. [30][31][32] The theoretical literature about the vibrational spectrum of the Zundel cation is quite vast, since its strong anharmonicity provides the ideal test-bed for theoretical methods. The PES computed at the level of coupled cluster theory and devised in Ref. 33, has been employed by a plethora of methods for vibrational calculations, such as vibrational configuration interaction (VCI), 34 diffusion Monte Carlo, 32,35 classical molecu-

show abstract

“On-the-fly” coupled cluster path-integral molecular dynamics: impact of nuclear quantum effects on the protonated water dimer

Cited by 33 publications

References 69 publications

Fully Quantum Description of the Zundel Ion: Combining Variational Quantum Monte Carlo with Path Integral Langevin Dynamics

Fully Quantum Description of the Zundel Ion: Combining Variational Quantum Monte Carlo with Path Integral Langevin Dynamics

Nuclear Quantum Effects in Water and Aqueous Systems: Experiment, Theory, and Current Challenges

Reduced rovibrational coupling Cartesian dynamics for semiclassical calculations: Application to the spectrum of the Zundel cation

Contact Info

Product

Resources

About