Discrete Molecular Dynamics

Florian R. Krajewski, Martin H. Müser

The commensurate Frenkel Kontorova (FK) model is studied using path-integral molecular dynamics (PIMD). We focus on the highly discrete case, in which the embedding potential has a much greater maximum curvature than the harmonic potential connecting two particles in the FK chain. When efficient sampling methods are used, the dynamical interpretation of adiabatic PIMD appears to represent quite accurately the true time correlation functions of this highly correlated many-body system. We have found that the discrete, quantum FK model shows different behavior than its continuum version. The spectral density does not show the characteristic omega-2Theta(omega-omegac) cusp of the continuum solution in the pinned phase (m>m(c)). We also identify a dynamical quantum hysteresis in addition to the regular classical hysteresis when an external force is applied to the FK chain. In the unpinned phase (m<or=m(c)), we find a linear response damping coefficient which is finite and only weakly dependent on temperature T at small values of T.

Bradley P. Feuston

Mo Sha, Bing Gu

Quantum geometrical molecular dynamics provides a quantum geometric picture for understanding reactive dynamics, especially excited-state conical intersection dynamics, and also a numerically exact method for strongly correlated electron-nuclear dynamics. However, there are substantial challenges in describing medium-sized molecules with tens of nuclear degrees of freedom. The main challenge is that it uses a discrete variable representation to discretize the molecular configuration space, and thus requires a tremendous number of quantum chemistry calculations to construct the electronic overlap matrix. Moreover, the expansion coefficients scale exponentially with molecular size for direct-product basis sets. We address these challenges by first introducing a coarse-grained local diabatic ansatz, followed by a tensor network representation of the expansion coefficients and the molecular time-evolution operator. With a full 24-dimensional demonstration using the pyrazine molecule, we show that such developments provide a highly accurate and computationally tractable method for high-dimensional, fully quantum, strongly coupled electron-nuclear dynamics from first principles.

H. Horiuchi

Jincheng Zhang

Quantum information has revolutionized various fields, and molecular dynamics (MD) simulations, while powerful, often struggle to capture the subtle complexities of molecular behavior. This paper introduces a novel computational framework, Quantum Information in Molecular Dynamics Calculation, leveraging quantum information and geometric constraints to provide a deeper understanding of molecular stability. We propose a new method for modeling molecular structure evolution, guided by the principles of quantum entanglement and geometric limitations, offering a significant advancement over traditional MD approaches. This framework aims to unveil the underlying geometric factors influencing molecular stability, ultimately providing insights into the fundamental principles governing molecular interactions.