Dear Colleague,

A number of bugs have been found in the Dissipative Particle Dynamics (DPD) code 
of DL_MESO 2.5.

The parallel import routines for Lees-Edwards periodic boundary conditions were 
discovered to be sending forces for particles in boundary halos to the incorrect 
processor nodes. This bug only appears when the system is divided into more than 
two subdomains in one or more dimensions. (Many thanks are due to Abouzar 
Moshfegh at the University of Sydney for bringing this bug to our attention.)

Incorrect calculations of the DPD conservative potentials were being carried 
out: this is a regrettable repeat of the bug reported in INFOMAIL 12 by Yaser 
Afshar at Johannes Gutenberg University. In addition, the incorrect forms of 
force and potential for hard surfaces with soft potentials were being applied, 
which were only correctly applied when the surface cutoff was set equal to 1 and 
should be analogous to the standard DPD conservative force and potential.

Calculations of runtimes in serial were occasionally incorrect (particularly 
when running in Windows) due to negative tick counts by the SYSTEM_CLOCK 
function used by the subroutine timchk in comms_module_ser.f90. (Parallel 
calculations are not affected since these use the MPI_WTIME function.) Many 
thanks are due to Ard van Bergen at Novidec for bringing our attention to this 
bug and proposing an appropriate fix.

Since there are several bug fixes to apply, we have therefore corrected the 
current version of DL_MESO and encourage all registered users to download 
DL_MESO again using the instructions they received on registration to obtain the 
corrected version of the software. The decryption password has not changed and 
thus re-registration is not required. Minor modifications have been made to the 
user manual, which can be downloaded from the main DL_MESO website, and the 
messages in both DPD and LBE codes encouraging citation of DL_MESO when 
publishing results have been updated to reflect departmental changes at STFC.

Michael Seaton
2013-01-31