Quantics: A general purpose package for Quantum molecular dynamics simulations

Abstract

Quantics is a general purpose program package to simulate the time-evolution of a molecular system by solving the time-dependent Schrödinger Equation The main code is based on the multi-configurational time-dependent Hartree (MCTDH) algorithm in various variants, including the powerful multilayer-MCTDH algorithm that has been used to propagate a wavefunction for up to 1000 degrees of freedom. MCTDH uses a contraction of traditional discrete basis set representations of the Hamiltonian and wavefunction, and Quantics includes a range of variable representation (DVR) grid basis sets and collocation methods. Input is via ascii text files and for molecules with analytical potential functions no programming is required. A library of potential functions is included to treat more complicated cases, and this can be added to by the user. The code also includes the variational multi-configurational Gaussian (vMCG) method that is based on a Gaussian Wavepacket expansion of the wavefunction. vMCG can be run in a "direct" manner (DD-vMCG), calculating the potential energy surfaces on-the-fly using a number of quantum chemistry programs. In addition to wavepacket propagation, Quantics can solve the time-independent Schrödinger equation for small systems and can solve the Liouville-von-Neumann equation to propagate density matrices. The Package includes auxiliary programs to help set up calculations and analyse the output. Quantics is a community code of the UK Collaborative Computational Project for Quantum Dynamics (CCPQ) and the European E-CAM project, an e-infrastructure for software development run by the Centre Européen de Calcul Atomique et Moléculaire (CECAM). Through this it has become a framework for general dynamics codes, for example enabling * Corresponding author.

Ultrafast pulse shaping modulates perceived visual brightness in living animals

“…Non-adiabatic quantum dynamics simulations were performed with the MCTDH wave packet propagation scheme ( 33 ) implemented within the Quantics package ( 34 ). The time-dependent Schrödinger equation was solved for the (time-dependent) Hamiltonian including the light-matter interaction term up to the dipole approximation.…”

Quantum dynamics of the ππ*/nπ* decay of the epigenetic nucleobase 1,5-dimethyl-cytosine in the gas phase

“…All electronic calculations were done with Gaussian 16 36 , LVC Hamiltonians were parameterized with an in-house code interfaced with Gaussian and available upon request and ML-MCTDH simulations were performed with Quantics. 37,38 3 Results 1 for CAM-B3LYP the character assigned to S 2 , S 5 and S 7 is qualitative, since they exhibit more than one contribution see also Figure S2 in the ESI.…”

PySurf: A Framework for Database Accelerated Direct Dynamics

“…In regions where calculations have already been performed, the fitting algorithm is used to interpolate the stored data and no further electronic structure calculations are needed, as implemented for the direct dynamics variational multiconfiguration Gaussian (dd-vMCG) approach in the Quantics program package. 6 , 10 In recent years, computational statistical learning methods (machine learning, neural networks, deep learning, unsupervised clustering, etc.) have found to provide very promising approaches to construct PE surfaces of high-dimensional systems.…”