The program FEFF6 is provided as a single source file, which contains a main program and all necessary subroutines. Simply compile and link on your system using a Fortran 77 compiler and your usual linker. The executable file produced is all you will need. The code requires about 3 megabytes to run on a VAX. Since most of this memory is data space, we expect it to require about this amount of memory on most machines. PC users, please see section below about DOS machines.
We have endeavored to make FEFF portable to most machines without any modification. If your machine does not reproduce the test output files chi.dat and feffNNNN.dat to high accuracy, some changes may be needed. Please report any problems or warning messages to the authors, as this will help us achieve full portability. If changes are needed, keep in mind the following points:
Floating point calculations must be done to precision 64 bits. Thus the code uses double precision variables throughout, i.e., real*8 for real numbers and complex*16 for complex numbers. If your machine uses 8 bytes for single precision floating point numbers (for example, Crays and some CDC machines), use the compiler option to ignore double precision statements in the code. This option is available (in various forms) on all Cray and CDC machines that we have seen. On the CRAY YMP at Ohio State, the compiler option to ignore double precision in the source code is
cf77 -c -Wf"-dp"
Code is written in ANSI FORTRAN 77, except that COMPLEX*16 variables are required. Since data type COMPLEX*16 is not part of the ANSI standard, minor compiler-dependent modification may be necessary. We have used the VAX extensions to ANSI FORTRAN 77 since they seem to be the most portable. The non-standard statements and intrinsic functions used are: COMPLEX*16 variables and arrays; DIMAG(arg) returns a double precision imaginary part of arg; DCMPLX(arg) returns a complex*16 version of arg; DBLE(arg) returns a double precision real part of arg; SQRT, EXP, ABS and other generic math functions are assumed to accept complex*16 arguments and return double precision or complex*16 results.
Files are opened with the OPEN statement. As the ANSI definition gives some leeway in how the OPEN statement interacts with the operating system, we have chosen file names and conventions that work on UNIX, VAX/VMS, IBM PCs (and clones) with MS FORTRAN, CRAY, MAC's and and CDC machines. It may be necessary to modify the open statements on other systems.
Because of the awkwardness of DOS, many users do not have FORTRAN compilers and many of those compilers are difficult to use with large codes. An executable version of FEFF for PCs is available. It has been compiled using Watcom's FORTRAN77 compiler which works with a DOS extender (DOS4GW) to use extended memory. You will need a PC with either a 386 and 387 math coprocessor or a 486 with the math coprocessor embedded in it (SX does not have this, DX does). You will also need about 3 Megabytes of RAM available, IN ADDITION TO whatever memory is used by DOS and memory-resident utilities. Please contact us if you need the PC executable. Special installation instructions for the PC version are in the READ.ME file on the PC distribution disk.
If you prefer your own compiler, or are using an operating system other than DOS, simply compile the source code using your FORTRAN compiler and linker as you would for any other machine.
Diskettes with an executable version of FEFF for MAC's are not yet available, but could be given sufficient demand. Please contact us if you need a MAC version please contact us.