CCL: Reaction Path Problems and Memory Questions in Q-CHEM

 Sent to CCL by: "Nathan Yoder" [n-yoder]*[northwestern.edu]
 Hi,
 I am having some problems running reaction path calculations in qchem on a
 "molecule" containing silicon, carbon, and hydrogen (30-40 atoms
 total)
 using DFT (B3LYP) with 6-31G** and 6-311G** basis sets.
 The calculations will run for a while, between 1-16 reaction path steps, and
 then will just quit, normally in the middle of an SCF cycle, although
 sometimes during the computation of the analytic gradient.
 Approximately 20% of the runs will give the error message:
      "Q-Chem fatal error occurred in module NewQAlloc.C, line 268:
 Unsuccessful malloc of 1678112 bytes of double storage"
 Which I took to mean a memory issue, so I played around with my memory
 settings.
 I generally have used a MEM_STATIC between 300 and 1000. (listed in the
 manual as # of MB) and a MEM_TOTAL of 1000-3000 (Also listed as MB).
 However, when I used MEM_TOTAL = 1000, I got the following error:
 "Q-Chem memory limit of 1000 bytes exceeded on allocation of 543232 bytes
 of
 INTEGER storage (chunk #721, address 610f6008)
  Q-Chem fatal error occurred in module NewQAlloc.C, line 316:   Q-Chem total
 memory limit exceeded"
 This indicates that that MEM_TOTAL is specified in BYTES, not MB ????  Does
 anyone have some insight into this?  I also tried setting MEM_TOTAL to  a
 really large value  (~1000000000) and still have the same problem.  The
 computer has over 2 GB of memory.
 In all of the cases, I am doing three consecutive Calculations:
 Transition structure --> Frequency --> Reaction Path.  Both the Transition
 Strucure search and the Frequency calculation run fine, the problem is
 always in the Reaction path calculation.
 Reaction Path Settings ($REM):
 EXCHANGE                B3LYP
 CORRELATION             None
 BASIS                   6-31G**
 JOBTYPE                 RPATH
 SCF_PRINT               0
 PRINT_ORBITALS          FALSE
 SCF_FINAL_PRINT         0
 MEM_TOTAL               1000
 MEM_STATIC              300
 SCF_GUESS               READ
 GEOM_OPT_HESSIAN        READ
 RPATH_MAX_CYCLES        200
 RPATH_COORDS            0
 RPATH_DIRECTION         1
 RPATH_TOL_DISPLACEMENT  50
 RPATH_MAX_STEPSIZE      450
 Any ideas are welcome....
 Nathan Yoder
 Northwestern University
 n-yoder#,#northwestern.edu