History
The QUANTICS package solves the time-dependent Schroedinger equation to simulate nuclear motion by propagating wavepackets. Various algorithms are possible, depending on the system of interest and the accuracy required. The focus of the package is the Multi-Configurational Time-Dependent Hartree (MCTDH) algorithm. The package grew out of the Heidelberg MCTDH Package.
QUANTICS has many new features compared to the older MCTDH packages. The main changes are the addition of the G-MCTDH algorithm and the direct dynamics DD-vMCG method. It also has an implementation of the real wavepacket propagation algorithm for scattering. The code is now Fortran 90 based with full dynamical allocation of memory. Parallelisation using OpenMP and MPI is made in many parts of the code. File structures have been updated. Version numbers are no longer appended to executable names. Automatic spline fits of data to provide potential functions.
Capabilities
- Grid-based Wavepacket Propagation
- standard MCTDH
- multi-layer MCTDH (ML-MCTDH)
- MCTDH including Gaussian Basis Functions (G-MCTDH)
- Numerically exact (standard) using SIL integrator
- Numerically exact using real WP propagation
- Gaussian Wavepacket Propagation using vMCG algorithm
- Direct dynamics using DD-vMCG
- Control calculations using either OCT or LCT.
- Eigenvalues and eigenfunctions
- Energy Relaxation to obtain the ground eigenstate
- Improved Relaxation to obtain eigenstates and eigenenergies of ground and/or low lying excited states.
- Direct diagonalisation of a Hamiltonian matrix using Lanczos
- Filter Diagonalisation to find the eigenvalues of a system from a wavepacket propagation.
- Density Matrix propagation for open or closed systems
- Potential energy function fitting to the MCTDH product form using the natural potential algorithm.
- Fitting a vibronic coupling model Hamiltonian.
In general, the input is made using ascii files. This enables a system to be set up with the minimum of effort. In particular, simple model system can be studied without any need to program. Options available include
- A wide range of DVRs to suit most situations, including 2D-DVRs/FBRs for the treatment of coupled theta/phi degrees of freedom.
- Operators may contain time-dependent terms, i.e. include a laser field.
- CAPs may be used to maintain the boundary conditions, and for the analysis of a system evolution.
- Propagation may be made on a cut through a potential function using a "point DVR".
Special features of the MCTDH wavepacket propagation are that:
- Non-adiabatic systems can be handled using the single- or multi-set formalismus.
- The CDVR method can be used for the evaluation of any multi-dimensional integrals