4,834 research outputs found
Fourth order real space solver for the time-dependent Schr\"odinger equation with singular Coulomb potential
We present a novel numerical method and algorithm for the solution of the 3D
axially symmetric time-dependent Schr\"odinger equation in cylindrical
coordinates, involving singular Coulomb potential terms besides a smooth
time-dependent potential. We use fourth order finite difference real space
discretization, with special formulae for the arising Neumann and Robin
boundary conditions along the symmetry axis. Our propagation algorithm is based
on merging the method of the split-operator approximation of the exponential
operator with the implicit equations of second order cylindrical 2D
Crank-Nicolson scheme. We call this method hybrid splitting scheme because it
inherits both the speed of the split step finite difference schemes and the
robustness of the full Crank-Nicolson scheme. Based on a thorough error
analysis, we verified both the fourth order accuracy of the spatial
discretization in the optimal spatial step size range, and the fourth order
scaling with the time step in the case of proper high order expressions of the
split-operator. We demonstrate the performance and high accuracy of our hybrid
splitting scheme by simulating optical tunneling from a hydrogen atom due to a
few-cycle laser pulse with linear polarization
Accelerating the Fourier split operator method via graphics processing units
Current generations of graphics processing units have turned into highly
parallel devices with general computing capabilities. Thus, graphics processing
units may be utilized, for example, to solve time dependent partial
differential equations by the Fourier split operator method. In this
contribution, we demonstrate that graphics processing units are capable to
calculate fast Fourier transforms much more efficiently than traditional
central processing units. Thus, graphics processing units render efficient
implementations of the Fourier split operator method possible. Performance
gains of more than an order of magnitude as compared to implementations for
traditional central processing units are reached in the solution of the time
dependent Schr\"odinger equation and the time dependent Dirac equation
Efficient GPU implementation of a Boltzmann‑Schrödinger‑Poisson solver for the simulation of nanoscale DG MOSFETs
81–102, 2019) describes an efficient and accurate solver for nanoscale DG MOSFETs
through a deterministic Boltzmann-Schrödinger-Poisson model with seven
electron–phonon scattering mechanisms on a hybrid parallel CPU/GPU platform.
The transport computational phase, i.e. the time integration of the Boltzmann equations,
was ported to the GPU using CUDA extensions, but the computation of the
system’s eigenstates, i.e. the solution of the Schrödinger-Poisson block, was parallelized
only using OpenMP due to its complexity. This work fills the gap by describing
a port to GPU for the solver of the Schrödinger-Poisson block. This new proposal
implements on GPU a Scheduled Relaxation Jacobi method to solve the sparse linear
systems which arise in the 2D Poisson equation. The 1D Schrödinger equation
is solved on GPU by adapting a multi-section iteration and the Newton-Raphson
algorithm to approximate the energy levels, and the Inverse Power Iterative Method
is used to approximate the wave vectors. We want to stress that this solver for the
Schrödinger-Poisson block can be thought as a module independent of the transport
phase (Boltzmann) and can be used for solvers using different levels of description
for the electrons; therefore, it is of particular interest because it can be adapted to
other macroscopic, hence faster, solvers for confined devices exploited at industrial
level.Project PID2020-117846GB-I00 funded by the Spanish Ministerio de Ciencia
e InnovaciĂłnProject A-TIC-344-UGR20 funded by European
Regional Development Fund
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