Re: PSF file format

From: Josh Vermaas (
Date: Fri Jun 04 2021 - 12:48:41 CDT

The best documentation on the format is *probably* the CHARMM
documentation, which is actually rather sparse.*IOFORM__;Iw!!DZ3fjg!uRPWqMKGW1780p7gOxom55ZPP9L4h9AHLa2pb7HsKx66nLOh7NH4vymgTxHM9_y3qw$

Basically, the first line of the PSF file dictates the field width. For
regular, non-extended PSFs, the header will look like:


In these files, you are limited to 4 characters for segnames and
atomtypes. CHARMM can also write (and VMD/NAMD can also read/write)
"extended" PSF files. The headers for these will look like:


This buys you 8 characters for segnames and atomtypes. NAMD/VMD also can
write space-delimited psf files, which are tagged as follows:


The NAMD/VMD version is the most flexible, since fields just need to be
separated by spaces, and for the most part psfgen/VMD will select this
option if the contents of the psf file demand it.


On 6/4/21 1:10 PM, Maximilian Ebert wrote:
> Dear list,
> Is there a resource which describes the PSF file format? I am many wondering about the max column width and if the width needs to be fixed or can changed when numbers get larger.
> Thanks

Josh Vermaas
Assistant Professor, Plant Research Laboratory and Biochemistry and Molecular Biology
Michigan State University;!!DZ3fjg!uRPWqMKGW1780p7gOxom55ZPP9L4h9AHLa2pb7HsKx66nLOh7NH4vymgTxF1980Jig$ 

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