This plugin reads and writes the "DCD" binary trajectory file format used by CHARMM, NAMD, and X-PLOR. The plugin performs automatic byte swapping to correctly read files written on machines with different endianness. The plugin supports reading of X-PLOR files, Charmm with fixed atoms and unit cell information, and NAMD files with fixed atoms and unit cell information. The DCD plugin writes trajectories in Charmm 24 format with unit cell data and without fixed atoms.
There's a description of the X-PLOR variation of the DCD format here:
The DCD format is structured as follows (FORTRAN UNFORMATTED, with Fortran data type descriptions):
HDR NSET ISTRT NSAVC 5-ZEROS NATOM-NFREAT DELTA 9-ZEROS `CORD' #files step 1 step zeroes (zero) timestep (zeroes) interval C*4 INT INT INT 5INT INT DOUBLE 9INT ========================================================================== NTITLE TITLE INT (=2) C*MAXTITL (=32) ========================================================================== NATOM #atoms INT ========================================================================== X(I), I=1,NATOM (DOUBLE) Y(I), I=1,NATOM Z(I), I=1,NATOM ==========================================================================
and the following describes the difference between X-PLOR and CHARMM formats:
Binary Trajectory Files
The file format is identical to the CHARMm-DCD format (Brooks et al. 1983, which can be read by QUANTA and a variety of other programs. The only exception is that the number of coordinate sets written to the trajectory file is explicitly written into the header of CHARMm-DCD files, whereas XPLOR writes a zero instead. Brief CHARMm format description