NANIWA series is a computational code for performing first principles quantum dynamics calculations. As the description implies, it is a quantum mechanical version of classical molecular dynamics (MD) calculations. A classical description of the system involved in, e.g., surface reactions (dissociative scattering, molecular scattering, dissociative adsorption, associative desorption, etc.) can be used, when quantum effects, such as tunneling, diffractions, and electronic excitations, play no essential role in the dynamics. In addition to this, the kinetic energy of, e.g., the impinging particle must be large enough, to ensure that the de Broglie wavelength is much smaller than the lattice constant of the solid (typically of the order of a few Angstroms), to be able to neglect interference phenomena. For hydrogen, with a translational energy of say 20 meV, the de Broglie wavelength is a few Angstroms. This dictates that we treat hydrogen as a quantum particle! For all the relevant surface reactions, there is a strong interaction between the impinging particle and the surface. This compounds the situation because interactions imply coupling between the internal degrees-of-freedom (e.g., vibration, rotation, and translation) of the particles immediately involved in the reaction. The vibrational motion, e.g., requires a quantum description, esp., when the respective quanta are large. Thus, the coupling between the internal degrees-of-freedom also requires a quantum mechanical description. As one would expect, the is computation code could also handle such problems as quantum transport, and quantum scattering in general.
For the first principles quantum dynamics calculation done by NANIWA series can be broken down into two main stages, viz.,
1) Determination of the effective potential energy (hyper-) surface
(PES) governing the reaction, based on the density functional
theory [1].
2) Solution of the corresponding multi-dimensional Schrodinger
equation for the reaction described by the above-determined
PES, based on the coupled-channel method [2,3] and the
concept of a local reflection matrix [4].
[1] P. Hohenberg, W. Kohn, Phys. Rev. 136 (1964) B864.
[2] W. Brenig, H. Kasai, Surf. Sci. 213 (1989) 170.
[3] H. Kasai, A. Okiji, Prog. Theor. Phys. Suppl. 106 (1991) 341.
[4] W. Brenig, T. Brunner, A. Gross, R. Russ, Z. Phys. B93 (1993) 91.
Source : http://www.dyn.ap.eng.osaka-u.ac.jp/web/naniwa_series.html
Tuesday, July 27, 2010
AkaiKKR (MACHIKANEYAMA)
AkaiKKR (MACHIKANEYAMA) is a software package used for first-principles calculation of the electronic structures of metals, semiconductors and compounds, within the framework of the local density approximation or generalized gradient approximation (LDA/GGA) of density functional theory.
The package, which features both high speed and high accuracy, uses the KKR–Green’s function method. This is an all-electron method and does not suffer from any serious truncation errors such as those associated with plane-wave cutoffs. Moreover, the CPA (coherent potential approximation) is integrated into the package making it applicable not only to crystals but also to disordered systems such as impurity systems, random substitutional alloys and mixed crystals. Since the Green’s function of the system is calculated, the package provides a good starting point for first-principles calculations of linear response theory, many-body effects, and so on.
The package has been in continuous development since the late 1970s and this development continues today. It is written in Fortran 77 and is completely self-contained (no additional libraries are required). It runs equally well on a notebook PC and a supercomputer. It can be used on any platform (UNIX, Linux, Mac OS, Windows etc.) where a Fortran compiler is installed. The memory required depends on the physical system to be calculated. For instance, a spin-polarized calculation of a system with a single atom per unit cell requires no more than a megabyte of memory. However, a larger system with, say, 20 atoms per unit cell, may require 1GB of memory.
Source : http://kkr.phys.sci.osaka-u.ac.jp/
The package, which features both high speed and high accuracy, uses the KKR–Green’s function method. This is an all-electron method and does not suffer from any serious truncation errors such as those associated with plane-wave cutoffs. Moreover, the CPA (coherent potential approximation) is integrated into the package making it applicable not only to crystals but also to disordered systems such as impurity systems, random substitutional alloys and mixed crystals. Since the Green’s function of the system is calculated, the package provides a good starting point for first-principles calculations of linear response theory, many-body effects, and so on.
The package has been in continuous development since the late 1970s and this development continues today. It is written in Fortran 77 and is completely self-contained (no additional libraries are required). It runs equally well on a notebook PC and a supercomputer. It can be used on any platform (UNIX, Linux, Mac OS, Windows etc.) where a Fortran compiler is installed. The memory required depends on the physical system to be calculated. For instance, a spin-polarized calculation of a system with a single atom per unit cell requires no more than a megabyte of memory. However, a larger system with, say, 20 atoms per unit cell, may require 1GB of memory.
Source : http://kkr.phys.sci.osaka-u.ac.jp/
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