[molpro-user] Linear Molecules and MP2 Frequnecies

[Simperler, Alexandra]

Dear fellow-users and Experts


I am working on a user-question I cannot resolve.



I tried converting into z-matrix, various Orient options etc.

The molecule is H-Br-Ar and is linear and being C*V MOLPRO picks up

correctly the largest Abelian subgroup, c2v all goes well for HF and MP2 single points but once it comes to Frequencies we get a complaint that x cannot be imposed, and noorient is on which I thought was switched of by Orient to start with.

We are using Molpro2012.1 btw



So my user tried:

***, some title

memory,400,m

symmetry,x,y;

orient,mass

ANG;

geomtyp=xyz

geometry={

3

  H          0.0000000000        0.0000000000       -2.8437425492

  Be         0.0000000000        0.0000000000       -1.5482621834

  Ar         0.0000000000        0.0000000000        0.4210358303

}

 gprint,orbitals;

 basis;

sp,h,aug-cc-pVDZ;c

spd,be,aug-cc-pwCVDZ;c

spd,ar,aug-cc-pwCVDZ;c

 end;

 {RHF;

wf,22,1,0;}

 pop;

 {RMP2

core,3,1,1,0}

 pop;

frequencies

 I personally tried a Z-Matrix approach:

 ***, H+BeAr aug-cc-pCVQZ CCSD(T) single point calculation at

 QCISD/aVQZ geometry !

memory,400,m

symmetry,x,y;

orient,mass,planexz

geometry={

H

Be , H , rhbe

Ar , Be , rbear , H , 180

}

 rhbe=1.29548 Ang

rbear=1.96930 Ang

 gprint,orbitals;

 basis;

sp,h,aug-cc-pVDZ;c

spd,be,aug-cc-pwCVDZ;c

spd,ar,aug-cc-pwCVDZ;c

 end;

 {RHF;

wf,22,1,0;}

 pop;

 {RMP2

core,3,1,1,0}

 pop;

frequencies



 and I ended up with:

 Computing numerical hessian using default procedure for command RMP2

 Symmetry elements for unique displacements: X  Y

  Using no symmetry in wavefunction calculations

  Running default procedure: RHF-SCF000  RMP2



  Numerically approximating hessian using central energy differences

  Task list generated. Total number of displacements:     24

  Attempt to include non-existent symmetry X  Because of noorient

 option, program will  not align to your requested symmetry elements

 Try again with different symmetry request  This error can also happen

in geometry optimizations that specify

   symmetry-breaking internal coordinates in terms of active variables

 User-specified symmetry elements: X,Y  Symmetry elements: Y  ? Error

 ? Symmetry error  ? The problem occurs in zmatrix.f:zmat_evaluate



 I am very puzzled because I don't know where the noorient comes from as we specify Orient in our inputs.

Is it something trivial we missed? Then I apologize kindly in advance.



Kind regards

Alex


Dr Alexandra Simperler FHEA
Software Sustainability Institute Fellow 2014

Department of Chemistry
Imperial College London
South Kensington
London SW7 2AZ
UK

Tel: +44 (0)20 759 41220
Email: a.simperler at imperial.ac.uk

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