QM/MM with Orca: Memory allocation failed

From: Gerard Rowe (GerardR_at_usca.edu)
Date: Wed Jul 18 2018 - 17:18:33 CDT

I'm having trouble getting hybrid QM/MM to run properly on my Linux machine. Every time I try to run a QM job using orca, namd dies with the message:

..

Info: Startup phase 15 took 0.000211954 s, 194.461 MB of memory in use
Info: Finished startup at 8.24108 s, 194.461 MB of memory in use

TCL: Minimizing for 100 steps
FATAL ERROR: Memory allocation failed on processor 0.

..

The relevant part of the configuration file:

QMSimsPerNode 1
QMBaseDir /dev/shm
qmConfigLine "! ZINDO/1 ENGRAD"
qmConfigLine "%output PrintLevel Mini Print\[P_Mulliken \] 1 Print\[P_AtCharges_M\] end"
qmMult 1 6
qmCharge 1 2.00
qmMult 2 6
qmCharge 2 2.00
qmSoftware orca
qmExecPath /usr/local/orca/orca_4_0_0_2_linux_x86-64/orca

I have defined two QM regions with 83 atoms each. I have no problem running namd2 or orca by themselves. I find it hard to believe that this semiempirical job is running out of memory on a system with 48 GB of RAM (569 MB in use at the start of the the job). This error occurs regardless of the number of processors

Is there some way to find out how much memory the program is attempting to allocate? Or is there a common reason this error may arise?

Thanks,
Gerard
University of South Carolina Aiken

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