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Manuscript Title: Density-functional theory calculations for poly-atomic systems: electronic structure, static and elastic properties and ab initio molecular dynamics.
Authors: M. Bockstedte, A. Kley, J. Neugebauer, M. Scheffler
Program title: fhi96md
Catalogue identifier: ACTF_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 107(1997)187
Programming language: Fortran.
Computer: IBM RS/6000.
Operating system: UNIX.
RAM: 32M words
Word size: 32
Keywords: Solid state physics, Crystal field, Density-functional, Local-density, Generalized gradient, Pseudopotentials, Plane-wave basis, Super cell, Molecular dynamics, Optimization structure, Total-energy, Potential-energy surface, Chemical binding, Diffusion surface, Reactions, Crystals, Crystals defects, Molecules.
Classification: 7.3.

Nature of problem:
In poly-atomic systems as for example molecules [1,2], crystals [3,4], defects in crystals [5,6], surfaces [7-9], it is highly desirable to perform accurate electronic structure calculations, without introducing uncontrollable approximations. This enables the predictive description of equilibrium properties as well as of non-equilibrium phenomena for a wide class of materials. Examples studied with the present code or its predecessor include meta-stabilities of defects [5-10}, surface reconstructions [11,12], diffusion [9,13], surface reactions [14-16], and phase transitions [17]. Molecular dynamics simulations combined with first-principles forces are a powerful tool to analyze the motion of the nuclei [13,18] and to accurately calculate thermodynamic properties such as diffusion constants and free energies [13]. The computer code described below enables this variey of investigations. It employs density-functional theory [20] together with the local- density approximation [21,22] or generalized gradient approximations [23-25] for the exchange-correlation functional.

Solution method:
Ab initio molecular dynamics on the Born-Oppenheimer surface is implemented by a two step method. In the first step the Kohn-Sham equation [26] is solved self-consistently to obtain the electron ground state and the forces on the nuclei. In a second step these forces are used to integrate the equations of motion for the next time step. The calculation of the total-energy and the Kohn-Sham operator in a plane- wave basis-set is done by the momentum-space method [27]. To solve the Kohn-Sham equation the package fhi96md employs the iterative schemes of Williams and Soler [28] and Payne et al [29]. We use the frozen-core approximation and replace the effect of the core electrons by norm- conserving pseudopotentials [30-33} in the fully separable form [34]. The equations of motion of the nuclei are integrated using standard schemes in molecular dynamics such as the Verlet algorithm. Optionally an efficient sructure optimization can be performed by a second order algorithm with a damping term.

Only pseudopotentials with s-, p-, and d-components are implemented. For highly correlated systems (e.g. f-electrons) the treatment of the exchange-correlation interaction is not appropriate. Relativistic effects are included via scalar relativistic pseudopotentials. The system is assumed to be non-magnetic, but a generalization of the program to magnetic states is straight forward.

Running time:
The test run took 6 min.

[1] W. Andreoni, F. Gygi and M. Parrinello, Phys. Rev. Lett. 68, 823 (1992).
[2] N. Troullier and J.L. Martins, Phys. Rev. B 46, 1754 (1992).
[3] G. Ortiz, Phys. Rev. B 45, 11328 (1992).
[4] A. Garcia et al., Phys. Rev. B 46, 9829 (1992).
[5] J. Dabrowski and M. Scheffler, Phys. Rev. B 40, 10391 (1989)
[6] S.B. Zhang and J.E. Northrup, Phys. Rev. Lett. 67, 2339 (1991).
[7] J.A. Alves, J. Hebenstreit and M. Scheffler, Phys. Rev. B 44, 6188 (1991).
[8] J. Neugebauer and M. Scheffler, Phys. Rev. B 46, 16067 (1992).
[9] R. Stumpf and M. Scheffler, Phys. Rev. B 53, 4958 (1996).
[10] M.J. Caldas, J. Dabrowski and M. Scheffler, Phys. Rev. Lett. 65, 2046 (1990).
[11] E. Pehlke and M. Scheffler, Phys. Rev. Lett. 71, 2338 (1993).
[12] O. Pankratov and M. Scheffler, Phys. Rev. Lett. 75, 701 (1995).
[13] M. Bockstedte and M. Scheffler, S. Phys. Chem. in print.
[14] A. Gross, B. Hammer, M. Scheffler and W. Brenig, Phys. Rev. Lett. 73, 3121 (1994).
[15] E. Pehlke and M. Scheffler, Phys. Rev. Lett. 74, 952 (1995).
[16] C. Stampfl and M. Scheffler, Phys. Rev. Lett. 78, 1500, (1996).
[17] N. Moll et al, Phys. Rev. B 52, 2550 (1995).
[18] A. Gross, M. Bockstedte and M. Scheffler, submitted to Phys. Rev. Lett.
[19] O. Sugino and R. Car, Phys. Rev. Lett. 74, 1823 (1995).
[20] P. Hohenberg and W. Kohn, Phys. Rev. 136B, 864 (1964).
[21] D.M. Ceperley and B.J. Alder, Phys. Rev. Lett. 45, 567 (1980).
[22] J.P. Perdew and A. Zunger, Phys. Rev. B 23, 5048 (1981).
[23] A.D. Becke, Phys. Rev. A 38, 3098 (1988).
[24] J.P. Perdew, Phys. Rev. B 33, 8822 (1986).
[25] J.P. Perdew et al, Phys. Rev. B 46, 6671 (1992).
[26] W. Kohn and J.L. Sham, Phys. Rev. 140A, 1133 (1965).
[27] J. Ihm, A. Zunger and M.L. Cohen, J. Phys. C 12, 4409 (1979).
[28] A. Williams and J. Soler, Bull. Am. Phys. Soc. 32, 562 (1987).
[29] M.C. Payne et al, Phys. Rev. Lett. 56, 2656 (1986).
[30] G.B. Bachelet, D.R. Hamann and M. Schluter, Phys. Rev. B 26, 4199 (1982).
[31] D.R. Hamann, Phys. Rev. B 40, 2980 (1989).
[32] N. Troullier and J.L. Martins, Phys. Rev. B 43, 1993 (1991).
[33] X. Gonze, R. Stumpf and M. Scheffler, Phys. Rev. B 44, 8503 (1991).
[34] L. Kleinman and D.M. Bylander, Phys. Rev. Lett. 48, 1425 (1982).