All files in deMon2k are opened with filenames. Throughout this Guide, the name used in the FORTRAN OPEN statement is referred to as the logical filename. These logical filenames are read by the program or created in the working directory.

Table 2: Physical and logical filenames in deMon. The I/O units are given in parentheses.
Physical Logical
Filename Filename Description Type
AUXIS AUX (1) Auxiliary function file ASCII
BASIS BAS (2) Basis set file ASCII
FFDS FFDS (5) Force field dataset file ASCII
deMon.inp INP (6) Input file ASCII
deMon.out OUT (7) Output file ASCII
deMon.geo GEO (8) Molecular geometry file ASCII NEW (9) New input file for restart ASCII
deMon.trj TRJ (10) Trajectory file ASCII
deMon.mol$^{a}$ MOL (11) MOLDEN input file ASCII
deMon.mkl$^{a}$ MOL (11) MOLEKEL input file ASCII
deMon.wfn$^{a}$ MOL (11) XAIM input file ASCII
deMon.qmm QMM (12) QM/MM interface file ASCII
deMon.xry XRY (13) XAS/XES analysis file ASCII
deMon.nbo NBO (14) NBO 5.G input file ASCII
deMon.pie PIE (15) VU control file ASCII
deMon.mem MEM (16) MEMORY file BINARY
deMon.rst RST (17) RESTART file BINARY
deMon.cub CUB (18) Embedding file ASCII LAT (19) Plot lattice file ASCII / BINARY EDU (20) Input file for reactant ASCII PRO (21) Input file for product ASCII

$^{a}$The I/O unit 11 is connected either to the MOLDEN, MOLEKEL or XAIM input file
depending on the VISUALIZATION (4.10.1) keyword. For the XYZ output the
MOLDEN file (deMon.mol) is used in all cases.

The logical files are connected to FORTRAN I/O units in the file fileio.h. Table 2 provides the logical and physical filenames used in the program.

From deMon2k 5.0 on the input file deMon.inp is modified into a fixed standard structure and, therefore, overwritten during program execution. The same applies for the geometry file deMon.geo. Thus, these files should be copied prior to program execution in order to preserve the original input formats.

Besides these files, special plot files may be created for the visualization of molecular fields, like the electronic density, electrostatic potential, etc., with VU [41]. These files are named according to the molecular field to be visualized. For example, a file RHO.bin is created for the visualization of the electronic density. The deMon.pie file is the VU control file and refers in this case to the RHO.bin file. If the job is executed by a script, care must be taken that these files are copied from the working directory to the output path and that the filenames are consistent with the ones in the deMon.pie file. These entries can also be modified manually in order to use the same VU control file for different molecular fields.