3D-GTDSE: A GPU-based code for solving 3D-TDSE in Cartesian coordinates

We present a graphics processing units (GPU) parallelization based three-dimensional time-dependent Schrödinger equation (3D-TDSE) code to simulate the interaction between single-active-electron atom/molecule and arbitrary types of laser pulses with either velocity gauge or length gauge in Cartesian coordinates. Split-operator method combined with fast Fourier transforms (FFT) is used to perform the time evolution. Sample applications in different scenarios, such as stationary state energies, photon ionization spectra, attosecond clocks, and high-order harmonic generation (HHG), are given for the hydrogen atom. Repeatable results can be obtained with the benchmark program PCTDSE, which is a 3D-TDSE Fortran solver parallelized using message passing interface (MPI) library. With the help of GPU acceleration and vectorization strategy, our code running on a single NVIDIA 3090 RTX GPU can achieve about 10 times faster computation speed than PCTDSE running on a 144 Intel Xeon CPU cores server with the same accuracy. In addition, 3D-GTDSE can also be modified slightly to simulate non-adiabatic dynamics involving the coupling of nuclear and electronic wave packets, as well as pure nuclear wave packet dynamics in the presence of strong laser fields within 3 dimensions. Additionally, we have also discussed the limitations and shortcomings of our code in utilizing GPU memory. The 3D-GTDSE code provides an alternative tool for studying the ultrafast nonlinear dynamics under strong laser fields.