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Manuscript Title: PLATTSUM: a Fortran program that evaluates electrostatic lattice sums by the planewise summation method.
Authors: J.A. Hernando, V. Massidda
Program title: PLATTSUM
Catalogue identifier: ABVT_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 22(1981)13
Programming language: Fortran.
Computer: IBM 370/158.
Operating system: OS/VS1, VM370/CMS.
RAM: 68K words
Word size: 32
Keywords: Crystallography, Electrostatics, Lattice sums, Crystal field, Lorentz factor, Electrostatic crystal Energy, Ewald potential, Planewise summation Method.
Classification: 8, 10.

Revision history:
Type Tit le Reference
correction 000A CORRECTION 07/09/81 See below

Nature of problem:
The calculation of the electrostatic potential due to a Bravais lattice of point charges presents several problems, of a practical as well as of a conceptual nature, coming from its convergence properties. Leaving aside the fact that the potential of an infinite charge distribution diverges, the numerical difficulties lie in the fact that the convergence of the sum is very slow.

Solution method:
We employ the planewise summation method (PSM), introduced by Nijboer and De Wette and recently generalized by Massidda and Hernando. The results given by this method correspond to a slab-shaped specimen. In this papaer we program the equations for calculating the electrostatic potential of a point-charge lattice and its spatial derivatives up to the fourth order. In all cases in addition to the shape-dependent value of the sum a shape-independent result is obtained. The latter is used to improve the speed of the computation and to verify the correctness of the calculation.

Restrictions:
If the field point is very near to (without coinciding with) a lattice site the series given by the PSM have a very slow convergence. For this reason the program in its present form excludes points contained in a small parallelepiped centred at each lattice site(~~10**-4 of the unit cell volume). If a calculation at a point very near to a lattice site is needed the restriction can be relaxed. There are no restrictions on the complexity of the unit cell, i.e. on the crystal symmetry or the number of the sublattices.

Unusual features:
It allows one to calculate the electrostatic potential (and its derivatives up to the fourth order) in a perfect crystal made of an arbitrary number of point-charge sublattices with arbitrary symmetry. It includes a method for a numerical check of the results.

CORRECTION SUMMARY
Manuscript Title: PLATTSUM: a Fortran program that evaluates electrostatic lattice sums by the planewise summation method. (C.P.C. 22(1981)13).
Authors: J.A. Hernando, V. Massidda
Program title: 000A CORRECTION 07/09/81
Catalogue identifier: ABVT_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 25(1982)111
Classification: 8, 10.