Please acknowledge the use of HALMD in your publications by citing our article:
P. H. Colberg and F. Höfling, Highly accelerated simulations of glassy dynamics using GPUs: Caveats on limited floating-point precision, Comp. Phys. Comm. 182, 1120 (2011) [Link].
The GPU backends of HALMD employ fixed-size cell and neighbour lists to accommodate for memory access pattern constraints. By default, a cell or neighbour list is allocated twice as many placeholders as the average expected number of particles. This may not suffice in case of large local density fluctuations, e.g. for unequilibrated systems.
Try lowering the --cell-occupancy value.
An infinite potential energy sum of one or more particles indicates that the integration time-step is too large.
Try lowering the --timestep value.