From owner-chemistry@ccl.net Thu Feb  9 14:20:48 2006
From: "Nathan Yoder n-yoder[*]northwestern.edu" <owner-chemistry[a]server.ccl.net>
To: CCL
Subject: CCL: Reaction Path Problems and Memory Questions in Q-CHEM
Message-Id: <-30833-060208133250-26211-oFUubBI8b8HYIDholY4Ciw[a]server.ccl.net>
X-Original-From: "Nathan Yoder" <n-yoder:+:northwestern.edu>
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Date: Wed, 8 Feb 2006 11:28:02 -0600
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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