[molpro-user] Problem with t2 Norm in MP2 calculations

[Christof Woell]

Problem with t2 Norm in MP2 calculations

I am doing MP2 calculations for a rather large system, a hydrocarbon on top 
of a metal cluster.
When computing the potential vs. distance curves everything works fine for 
large distances.
When the distance gets smaller,  I get on the MP2-level the following 
errror message:
---------------------------------------------
  Multipassing necessary in transformation. To avoid, increase memory 
by    3195515025 words
  Integral transformation finished. Total CPU:******* sec, 
npass=  5  Memory used: 979.16 MW
  Memory needed for MP2:                       1.13 MW
  UNREASONABLE NORM. CALCULATION STOPPED
  Norm of t2 vector:     53.77169283      P-energy:    -3.32278637
  Reference energy                   -1303.594849374982
  Correlation energy                    -3.322786371429
  !MP2 ENERGY                        -1306.917635746411
  ERROR EXIT
  CURRENT STACK:      MAIN
----------------------------------------------------------------------------------------

At the same time, the SCF-calculations converges fine. When I decrease the 
distance further, the t2-norm gets even larger.
Does anyone have an idea? Could this arise from linear dependencies in the 
basis set?

Any advice will be appreciated. Thank you.

Christof Wöll

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Prof. Dr. Christof Wöll
Physikalische Chemie I, Ruhr-Universitaet Bochum, 44780 Bochum

Tel  : ++49(0)234-322-5529  E-Mail: woell at pc.ruhr-uni-bochum.de
Fax  : ++49(0)234-3214-182  WWW:    http://www.pc.ruhr-uni-bochum.de
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