Subject: "MULTIMODE"; a code to obtain accurate rovibrational energy levels for many-mode molecules

From: Eugene Leitl <[email-masked]>
Date: Thu, 18 May 2000 14:05:19 -0700 (PDT)

From: Joel Bowman <[email-masked]>
Sender: [email-masked]
To: [email-masked]
Subject: no subject (file transmission)
Date: Thu, 18 May 2000 11:25:16 -0400 (EDT)

                            Program announcement

"MULTIMODE"; a code to obtain accurate rovibrational energy levels for many-mode molecules by:
   
S. Carter,  39, Grove Hill, Caversham, Reading RG4 8PS, UK
J.M. Bowman,  Department of Chemistry, Emory University, Atlanta GA 30322, USA
and contributions from N.C. Handy,   Department of Chemistry, Lensfield Road, 
Cambridge CB2 1EW, UK
   
   "MULTIMODE" is a near-variational procedure for the calculation of
   rovibrational energies of polatomic molecules, adsorbates and clusters.
   The method is based on the Watson normal coordinate hamiltonian for
   non-linear molecules, and proceeds via vibrational SCF and rovibrational
   CI steps.  The complete hamiltonian is used at all times, but approximations
   are made in order to integrate the potential and coriolis terms.  These terms
   are included as N-mode expansions in the normal coordinates, but are 
   truncated at the 4-mode terms.  It has been demonstrated that higher terms
   are insignificant compared with the inaccuracies in the potential itself.
   The method has been thoroughly tested for a variety of  triatomic and
   tetraatomic molecules and, in particular, against exact variational results
   for H2CS (6 modes, ref. 1) and more recently it has been applied to 
   CH4 (9 modes, ref. 2).  In both cases, excellent convergence
   has been achieved for all of the low-lying vibrational levels.
   
  "MULTIMODE" can be used in less accurate calculations, for example at the SCF
  level alone, or in SCF-CI calculations, where specified numbers of vibrational
  (non-orthogonal) SCF functions are used in a vibrational CI basis.   These
  methods also allow for an adiabatic rotation scheme, which gives reasonable
  values for rotational constants, in particular.
   
  "MULTIMODE" is currently being extended to include the Watson 
  hamiltonian for linear molecules, and also to include the Miller-Adams-Handy
  Reaction Path hamiltonian in order to describe a single large-amplitude
  coordinate, for example the torsion in H2O2.  This will widen the scope of
  molecules that can be handled.
   
   information:  www.emory.edu/CHEMISTRY/faculty/bowman/multimode
   
   enquiries:    [email-masked]
   
   References
   ----------
  1.  S. Carter, J.M. Bowman and N.C.Handy; Theor. Chem. Accts., 100, 191 (1998)
  2.  S. Carter and J.M. Bowman; J. Phys. Chem. 104, 2443 (2000)