[molpro-user] Transition dipole moment, phase convention

[Michael Hayes]

Dear Molpro users,

I am trying to calculate a smooth transition dipole moment surface
between the lowest two A' states of H3+. However, I believe that the
output does not maintain a consistent phase convention for the two
electronic wavefunctions, resulting in a transition dipole moment that
sometimes switches sign abruptly between adjacent nuclear geometries.

Does anyone know of a way to automatically ensure that the phases of
the wavefunctions remain consistent between single point calculations?

My input file is attached at the end. Any help would be greatly
appreciated.

Michael Hayes

! The bond coordinates x(i),y(i) and z(i) are specified in a separate
! input file
thresh=0.00000001
do i=1,npts
  r1=x(i)
  r2=y(i)
  r3=z(i)
  rrr=sqrt((r1**2+r2**2-0.5*r3**2)/2.0)
  sss=r3
  cost=(r1**2-rrr**2-0.25*r3**2)/(rrr*sss)
  sint=sqrt(1.0-cost**2)
  if(abs(cost-1.0).lt.thresh) sint=0.0
  xx1=rrr+sss*cost/2
  yy1=sss*sint/2
  xx2=rrr-sss*cost/2
  yy2=-sss*sint/2
  geomtyp=zmat
  geometry={
    H,, 0.0, 0.0, 0.0
    H,, xx1, yy1, 0.0
    H,, xx2, yy2, 0.0
  }
  GEXPEC,DM;
  TRAN,DM;
  aoint,c_seward=0
  multi;occ,3;wf,2,1,0;state,2;
  CI;state,2;option,nstati=5;
  e1(i)=energy(1)
  e2(i)=energy(2)
  dx1(i)=dmx(1)
  dx2(i)=dmx(2)
  dx12(i)=trdmx(1)
  dy1(i)=dmy(1)
  dy2(i)=dmy(2)
  dy12(i)=trdmy(1)
enddo