View source for Resgrg:comp-photo-version control-codes

This page explains the local modifications made to the Gaussian code by the group.  Hopefully it'll also explain
how to use them as well.

==The codes==

===Shaopeng===
This is a replacement for the existing matrix element generator (hereafter known as the Klene code) 
that is used for large (number of orbitals > 8)
CASSCF calculations.  If your job shows <code>SME calculated on fly</code> then it's using this path.

The Shaopeng code computes the same matrix elements but does it faster, and in a way that allows certain compiler
optimisations to be used.  The result should be an approximate 4X speedup, depending on the job and the architecture that you're running on.  This speedup comes at a cost of memory.  The algorithm is much more demanding of memory and this extra demand scales with the number of processors.

How to use it: by default l510 will make a decision on whether to use the Klene code path or the Shaopeng based on the problem size and the amount of memory and processors allocated.  You can force one code path over the other 
with the IOP(5/139=x) where:

{|
! Iop(5/139)
! Effect
|-
| 0
| Default, choose code path automatically
|-
| 1
| Force Klene code path
|-
| 2
| Force Shaopeng code path
|}

===Seamfollowing===

Dunno

===ONIOM Freq===

Shows contributions of sub-calculations to the ONIOM frequency according to the formula:

<math>(f^{ONIOM}_{i})^{2} = (f^{'high}_{model,i})^{2} + (f^{'low}_{real,i})^{2}-(f^{'low}_{model,i})^{2}</math>

The sub-calculation terms are obtained from the diagonal elements after transformation of the sub-Hessians with the ONIOM normal modes.
This gives the curvature of each sub-calculation PES with respect to the ONIOM mode so we can see how the ONIOM PES is determined
i.e. if a transition state located using ONIOM has an imaginary mode comprised of three real sub-components, then the transition state is a result of the extrapolation and is not consistent with the underlying calculations. This result suggests caution should be used as the stationary point may be spurious.
                                                                            
The ONIOM frequency analysis is called using IOp(7/123=1):

     IOp(123) ... Print partitioning of ONIOM vibrational frequencies                    
                  into contributions from individual sub-calculations.                   
                  see Vreven et al. JCTC, 2012, DOI: 10.1021/ct300612m                   
            0 ... Don't do ONIOM frequency analysis                                      
            1 ... Do ONIOM frequency analysis

Example output:

 Mode    Low-Real   Low-Model  High-Model       Total                                     
    1   2181.3672    433.6860    231.1949   2150.2862                                     
    2   4029.7184   2543.4278   2310.9318   3887.1598                                     
    3   4317.3046    869.1994    789.5792   4301.9818