Free initio software for linux

FFTW is a fast C FFT library.
FFTW is a C subroutine library for computing the discrete Fourier transform (DFT) in one or more dimensions, of arbitrary input size, and of both real and complex data (as well as of even/odd data, i.e. the discrete cosine/sine transforms or DCT/DST). We believe that FFTW, which is free software, should become the FFT library of choice for most applications.
Our benchmarks, performed on on a variety of platforms, show that FFTWs performance is typically superior to that of other publicly available FFT software, and is even competitive with vendor-tuned codes. In contrast to vendor-tuned codes, however, FFTWs performance is portable: the same program will perform well on most architectures without modification.
Hence the name, "FFTW," which stands for the somewhat whimsical title of "Fastest Fourier Transform in the West."
The FFTW package was developed at MIT by Matteo Frigo and Steven G. Johnson. Server co-location is thanks to the Joannopoulos Ab-Initio Physics group.
Main features:
- Speed. (Supports SSE/SSE2/3dNow!/Altivec, new in version 3.0.)
- Both one-dimensional and multi-dimensional transforms.
- Arbitrary-size transforms. (Sizes with small prime factors are best, but FFTW uses O(N log N) algorithms even for prime sizes.)
- Fast transforms of purely real input or output data.
- Transforms of real even/odd data: the discrete cosine transform (DCT) and the discrete sine transform (DST), types I-IV. (New in version 3.0.)
- Efficient handling of multiple, strided transforms. (This lets you do things like transform multiple arrays at once, transform one dimension of a multi-dimensional array, or transform one field of a multi-component array.)
- Parallel transforms: parallelized code for platforms with Cilk or for SMP machines with some flavor of threads (e.g. POSIX). An MPI version for distributed-memory transforms is also available, currently only as part of FFTW 2.1.5.
- Portable to any platform with a C compiler. Documentation in HTML and other formats.
- Both C and Fortran interfaces.
- Free software, released under the GNU General Public License (GPL, see FFTW license). (Non-free licenses may also be purchased from MIT, for users who do not want their programs protected by the GPL. Contact us for details.) (Also see the FAQ.)
Enhancements:
- This release fixes the --enable-portable-binary option in the configure script.
- It fixes thread compilation on AIX.
- Configure now detects Core/Duo arch.
- Altivec detection has been fixed.

octopus project is a program aimed at the ab initio virtual experimentation on a hopefully ever increasing range of systems types.
Electrons are describe quantum-mechanically within the Density-Functional Theory (DFT), in its time-dependent form (TDDFT) when doing simulations in time. Nuclei are described classically as point particles.
Electron-nucleus interaction is described within the Pseudopotential approximation.
Enhancements:
- The complex executable is gone, and all the work is done by the normal (a.k.a. real) executable.
- The type of the wavefunctions is selected automatically according to the input file.
- Dynamical polarizabities are calculated using linear response theory.
- Basic support for full potential all electron species.
- The texinfo documentation has been obsoleted and replaced by an online wiki based documentation.