Which quantum statistics–classical dynamics method is best for water?

Abstract

We make a systematic comparison of TRPMD, CMD, QCMD and LSC-IVR by calculating the infrared spectrum of water in its gas, liquid and ice phases.

Anharmonic spectral features via trajectory-based quantum dynamics: A perturbative analysis of the interplay between dynamics and sampling

“…As mentioned by the authors of Ref. 16, these results raise the question of why ring-polymer methods (QCMD, CMD, and RPMD) are unable to reproduce overtones and combination bands. This failing cannot be attributed to a lack of real-time coherence, since this approximation is also present in LSC-IVR.…”

“…This system has also been considered for a similar analysis by Benson et al in ref. 16 and 29, that provide a comparison of the IR absorption spectra obtained from PI-based methods (TRPMD, CMD and the more recent QCMD), from LSC-IVR (using LGA for the Wigner density sampling) and from a quasi-exact wavefunction-based resolution (using the DVR method 56 ). The authors show that PI approaches do not capture the intensity of overtones and combination bands correctly while LSC-LGA is in much better agreement with the quasi-exact reference (although with broadened spectral lineshapes).…”

“…This occurs, for example, in reactions involving proton transfer [6][7][8] or showing significant isotope effects [9][10][11][12][13][14] . The spectroscopy of ice and water is also affected by NQEs [15][16][17] . On a different scene, the rapid developments in the area of quantum computers motivate accurate simulations, for example, of coherence effects in qbits and of the influence of the environment on quantum components.…”

“…Trajectory-based methods have been successfully applied to simulate the behaviour of condensed matter systems, but it is commonly assumed that they are intrinsically unable to capture phenomena such as overtones, combination bands or Fermi resonances because these are believed to derive predominantly from quantum coherence, and thus to be impossible to capture via classical propagation. Only very recently, numerical tests have been performed to compare the performance of different PI or semi-classical methods in reproducing combination bands in the important case of water and ice spectroscopy 16 . These exploratory calculations indicate that an interesting development of CMD, the so-called quasi-CMD 28 (QCMD) method, and LSC-IVR accurately describe the fundamental bands in the spectrum of gas and liquid-phase water and in ice.…”

Dynamics & Spectroscopy with Neutrons—Recent Developments & Emerging Opportunities

“…These approximate approaches may suffer from issues, like the curvature problem in centroid MD [ 379 ], which is particularly severe at low temperatures [ 380 ], or ZPE-leakage [ 381 ] and spurious resonances occurring in TRPMD [ 381 , 382 ]. Recently, Althorpe and co-workers have proposed an alternative approach called Quasi-Centroid MD (QCMD) which circumvents these limitations [ 380 , 383 ]. More rigorous Path-Integral MD (PIMD) approaches have also been developed, yet at a clear computational cost [ 384 , 385 , 386 , 387 ].…”