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Manuscript Title: Gibbs2: A new version of the quasi-harmonic model code. I. Robust treatment of the static data.
Authors: A. Otero-de-la-Roza, Víctor Luaña
Program title: ASTURFIT
Catalogue identifier: AEIY_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 182(2011)1708
Programming language: GNU Octave.
Computer: Workstations.
Operating system: Unix, GNU/Linux.
Keywords: Equations of State in Solids, Equilibrium Properties of Solids, Data Analysis, Treatment of Noisy Data, Discontinuous Data, Thermal Effects.
PACS: 07.05.Bx, 71.15.-m, 64.10.+h 65.40.-b 64.30.Jk.
Classification: 4.9.

External routines: The GSL and OPTIM packages from the octaveforge site (http://octave.sourceforge.net/).

Nature of problem:
Fit the total energy versus volume data of a solid to a continuous function and extract the equilibrium properties and the derivatives of the energy, with an estimation of the error introduced by the fitting procedure.

Solution method:
The use of averages of strain polynomials allow a robust and reliable representation of the energy curve and its derivatives, together with a statistical estimation of the goodness of the calculated properties.

Additional comments:
The techniques discussed have been implemented in GIBBS2, to be included with the second part of this article. Included here is the OCTAVE implementation of the routines, useful for interactive work and also for the creation of independent scripts. Some representative examples are included as test cases with a collection of datasets, test scripts, and model outputs.

Running time:
Seconds at most in routine uses of the program. Special tasks like the bootstrap analysis may take up to some minutes.