Subject: ONIOM DFT/AM1 calculations with Osmium

From: Gali Drudis i Sole <[email-masked]>
Date: Fri, 8 Mar 2002 18:57:03 +0100

I am trying to calculate a large molecule using a hybrid method. The
molecule contains an osmium tetroxide plus a large organic
residue. The procedure will involve an ONIOM calculation using a small
DFT region plus a large semiempiric region. However, the ONIOM method
requires that the whole molecule be described by the low method, AM1
in this case. The problem arises when I try to calculate the whole
molecule using AM1.

To my unluck, not only is Osmium not parametrized in Gaussian98.A9,
but the VSTO-3G basis does not suppor athoms greater than N=54 (osmium
has an atomic number of 76). To make things worse, looking inside the
code, every athom with N>54 is exchanged by Xe in link 301. But Xenon
is described without d orbitals, and therefore I get the following
error:

========================================================================
 (Enter /QFsoft/g98/l301.exe)
 Standard basis: VSTO-3G (5D, 7F)
 Atomic number  76 exceeds maximum of  54 in STO -- maximum used.
 There are     5 symmetry adapted basis functions of A'  symmetry.
 There are     1 symmetry adapted basis functions of A"  symmetry.
 Crude estimate of integral set expansion from redundant integrals=1.000.
 Integral buffers will be    262144 words long.
 Raffenetti 1 integral format.
 Two-electron integral symmetry is turned on.
     6 basis functions       18 primitive gaussians
     5 alpha electrons        5 beta electrons
       nuclear repulsion energy         5.0493269225 Hartrees.
 Leave Link  301 at Fri Mar  8 18:49:55 2002, MaxMem=    6291456 cpu:       0.1
 (Enter /QFsoft/g98/l401.exe)
 Simple Huckel Guess.
 NBasis=   6 NMin=  11 so simple Huckel guess is impossible.
 Error termination via Lnk1e in /QFsoft/g98/l401.exe.
========================================================================

Link 401 complains that not enough basis functions are available. Do
you have any hint how I could solve this problem?

Many thanks in advance,

-- 
    Galí Drudis i Solé
    [email-masked]
     
     Universitat Autònoma de Barcelona
     Unitat de Química
     Lab: C7/157
     Tel: +34 93-581.28.14
     Fax: +34 93-581.29.20