Finite temperature quantum statistics of H3+ molecular ion

Kylänpää, Ilkka; Rantala, Tapio T.

doi:10.1063/1.3464758

Cited by 16 publications

(7 citation statements)

References 29 publications

(72 reference statements)

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“…( 6) to T = 0 is given by 2 √ π a 1 a 2 + a 3 . The corresponding data for B and C is presented in Table IV together with quadratically extrapolated total energies and appropriate references [24,[30][31][32][33]. The raw data and the fitting coefficients can be found in the Supplementary material.…”

Section: Resultsmentioning

confidence: 99%

Static field-gradient polarizabilities of small atoms and molecules at finite temperature

Tiihonen

Kylänpää

Rantala

2017

The Journal of Chemical Physics

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In this work, we propose new field-free estimators for static field-gradient polarizabilities in finite temperature PIMC simulation. Namely, dipole-quadrupole polarizability A, dipole-dipolequadrupole polarizability B and quadrupole-quadrupole polarizability C are computed for several up to two-electron systems: H, H − , He, Li + , Be 2+ , Ps2, PsH, H + 2 , H2, H + 3 and HeH + . We provide complementary data for ground state electronic properties within the adiabatic approximation, and demonstrate good agreement with available values in the literature. More importantly, we present fully non-adiabatic results from 50 K to 1600 K, which allow us to analyze and discuss strong thermal coupling and rovibrational effects in total field-gradient polarizabilities. These phenomena are most relevant but clearly overlooked, e.g., in the construction of modern polarizable force field models. However, our main purpose is demonstrating the accuracy and simplicity of our approach in a problem that is generally challenging.

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Section: Resultsmentioning

confidence: 99%

Static field-gradient polarizabilities of small atoms and molecules at finite temperature

Tiihonen

Kylänpää

Rantala

2017

The Journal of Chemical Physics

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“…There are many other approaches to treating non-adiabatic effects, such as path-integral molecular dynamics, [57][58][59][60][61][62][63] path-integral Monte-Carlo, [64][65][66] quantum Monte-Carlo 67,68 and wavepacket methods, [69][70][71][72][73] however, as they are not directly related to current work, we will not discuss them in detail.…”

Section: Introductionmentioning

confidence: 99%

Molecular second-quantized Hamiltonian: Electron correlation and non-adiabatic coupling treated on an equal footing

Sibaev

Polyak

Manby

et al. 2020

The Journal of Chemical Physics

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We introduce a new theoretical and computational framework for treating molecular quantum mechanics without the Born-Oppenheimer approximation. The molecular wavefunction is represented in a tensor-product space of electronic and vibrational basis functions, with electronic basis chosen to reproduce the mean-field electronic structure at all geometries. We show how to transform the Hamiltonian to a fully second quantized form with creation/annihilation operators for electronic and vibrational quantum particles; paving the way for polynomial-scaling approximations to the tensor-product space formalism. In addition, we make a proof-of-principle application of the new ansatz to the vibronic spectrum of C 2 .

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“…Similar empirical-potential and tight-binding path-integral approaches have been applied in solids [6][7][8][9][10] . In more general situations, the disentanglement of the electronic and ionic degrees of freedom might not be possible [11][12][13][14][15][16] and accurate approaches have been developed to treat the full electron-ion problem [17][18][19][20][21][22][23][24][25] . With these approaches, however, it is presently difficult to go beyond smaller systems.…”

Section: Introductionmentioning

confidence: 99%

“…Then the partition function, which yields the same averages as the one in Eq. (25), can be constructed as:…”

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confidence: 99%

Density functional theory beyond the Born-Oppenheimer approximation: Accurate treatment of the ionic zero-point motion

2018

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We introduce a method to carry out zero-temperature calculations within density functional theory (DFT) but without relying on the Born-Oppenheimer (BO) approximation for the ionic motion.Our approach is based on the finite-temperature many-body path-integral formulation of quantum mechanics by taking the zero-temperature limit and treating the imaginary-time propagation of the electronic variables in the context of DFT. This goes beyond the familiar BO approximation and is limited from being an exact treatment of both electrons and ions only by the approximations involved in the DFT component. We test our method in two simple molecules, H 2 and benzene.We demonstrate that the method produces a difference from the results of the BO approximation which is significant for many physical systems, especially those containing light atoms such as hydrogen; in these cases, we find that the fluctuations of the distance from its equilibrium position, due to the zero-point-motion, is comparable to the interatomic distances. The method is suitable for use with conventional condensed matter approaches and currently is implemented on top of the periodic pseudopotential code SIESTA. arXiv:1804.10852v4 [cond-mat.mtrl-sci]

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Finite temperature quantum statistics of H3+ molecular ion

Cited by 16 publications

References 29 publications

Static field-gradient polarizabilities of small atoms and molecules at finite temperature

Static field-gradient polarizabilities of small atoms and molecules at finite temperature

Molecular second-quantized Hamiltonian: Electron correlation and non-adiabatic coupling treated on an equal footing

Density functional theory beyond the Born-Oppenheimer approximation: Accurate treatment of the ionic zero-point motion

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