This directory contains a few fortran programs for calculating
the electronic structure of the two-electron systems He and H2. 

In the H2 program, a call is made to the error function. In many
modern f77 compilers, this function is implemented, so that a simple
call to "erf" instead of "derf" is ok on line 181 of the file h2.f 
(double precision function F(x)).
Because on some compilers, the error function is missing, 
I have included a C function (in program erf.c), which provides
the correct fortran interface to the c-error function.
Good error function routines wriiten in f77 can be found on 
www.netlib.org

Jos Thijssen
