Dynamical pruning of the multiconfiguration time-dependent Hartree method (DP-MCTDH): An efficient approach for multidimensional quantum dynamics

Abstract

We present two strategies for combining dynamical pruning with the multiconfiguration time-dependent Hartree method (DP-MCTDH), where dynamical pruning means on-the-fly selection of relevant basis functions. The first strategy prunes the primitive basis that represents the single-particle functions (SPFs). This is useful for smaller systems that require many primitive basis functions per degree of freedom, as we will illustrate for NO${}_2$. Furthermore, this allows for higher-dimensional mode combination and partially lifts the sum-of-product-form requirement onto the structure of the Hamiltonian, as we illustrate for nonadiabatic 24-dimensional pyrazine. The second strategy prunes the set of configurations of SPF at each time step. We show that this strategy yields significant speed-ups with factors between 5 and 50 in computing time, making it competitive with the multilayer MCTDH method.

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• Time Evolution of ML-MCTDH Wavefunctions II: Application of the Projector Splitting Integrator
• Dynamical Pruning of the Non-Equilibrium Quantum Dynamics of Trapped Ultracold Bosons
• 2500 vibronic eigenstates of the NO${}_3$ radical
• Benchmarking vibrational spectra: 5000 accurate eigenstates of acetonitrile using tree tensor network states
• Resonance dynamics of DCO ($\tilde{X}{}^2{A}^{\prime }$) simulated with the dynamically pruned discrete variable representation (DP-DVR)
• Control of concerted back-to-back double ionization dynamics in helium
• Accurate, full-dimensional computations of thousands of complex vibrational eigenstates with tree tensor network states