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Manuscript Title: turboTDDFT - a code for the simulation of molecular spectra using the Liouville-Lanczos approach to time-dependent density-functional perturbation theory
Authors: Osman Baris Malcioglu, Ralph Gebauer, Dario Rocca, Stefano Baroni
Program title: turboTDDFT
Catalogue identifier: AEIX_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 182(2011)1744
Programming language: Fortran 95.
Computer: Any computer architecture.
Operating system: GNU/Linux, AIX, IRIX, Mac OS X, and other UNIX-like OS's.
Keywords: Time-dependent density-functional theory, Density-functional perturbation theory, Quantum ESPRESSO, Optical spectra, Linear response, Liouville equation, Lanczos method.
Classification: 16.2, 16.6, 7.7.

External routines: turboTDDFT is a tightly integrated component of the Quantum ESPRESSO distribution and requires the standard libraries linked by it: BLAS, LAPACK, FFTW, MPI.

Nature of problem:
Calculation of the optical absorption spectra of molecular systems.

Solution method:
The dynamical polarizability of a system is expressed in terms of the resolvent of its Liouvillian super-operator within time-dependent density-functional theory, and calculated using a non-Hermitean Lanczos method, whose implementation does not require the calculation of any virtual states. Pseudopotentials (both norm-conserving and ultrasoft) are used in conjunction with plane-wave basis sets.

Restrictions:
Spin-restricted formalism. Linear-response regime. No hybrid functionals. Adiabatic XC kernels only.

Unusual features:
No virtual orbitals are used, nor even calculated. A single Lanczos recursion gives access to the whole optical spectrum.

Running time:
From a few minutes for small molecules on serial machines up to many hours on multiple processors for complex nanosystems with hundreds of atoms.