Elsevier Science Home
Computer Physics Communications Program Library
Full text online from Science Direct
Programs in Physics & Physical Chemistry
CPC Home

[Licence| Download | New Version Template] aecz_v1_0.tar.gz(268 Kbytes)
Manuscript Title: Gmat Version 1.0. A software tool for the computation of the rovibrational G matrix.
Authors: M. E. Castro, A. Niño, C. Muñoz-Caro
Program title: Gmat
Catalogue identifier: AECZ_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 180(2009)1183
Programming language: Standard C++.
Computer: All running Linux/Windows.
Operating system: Linux, Windows.
Keywords: Rovibrational G matrix, Principal inertia axes, Vibrational coordinates, Object-oriented programming.
PACS: 31.15.xv, 33.15.Mt, 33.20.Vq, 02.60.Jh.
Classification: 16.2.

Nature of problem:
Computation of the rovibrational G matrix in molecules of any size. This allows the building of arbitrary rovibrational Hamiltonians. It must be possible to obtain the input data from the output files of standard electronic structure codes. In addition, the program should handle the large number of files generated in massive explorations of molecular potential energy hypersurfaces. In these cases, Gmat will provide the G matrix as a function of the molecular structure.

Solution method:
To reach its objectives, Gmat has been organized in two components: an interface and a functional part. This organization allows for separating the input/output tasks, which are dependent on the human-machine interaction model selected, from the functional requirements, which are not. An object-oriented approach has been used in both parts. In the interface, polymorphism is used to allow the data acquisition from output files of different electronic structure codes. In the functional part, Gmat computes numerically the derivatives of the Cartesian coordinates respect to the vibrational coordinates needed to build the G matrix. Extremely accurate numerical derivatives are obtained in a double procedure. First, the truncation plus roundoff errors are minimized in the central differences expression. Second, the result is embedding in a nine levels Richardson extrapolation process. In the present version, the program allows the use of internal coordinates as vibrational coordinates, with the principal axes of inertia as body-fixed system.

Running time:
Sample test runs provided with the distribution take a few seconds to execute.