QChem

Q-Chem is a commercial quantum chemistry package available for use in our group.

Fragment Guesses with multiple bases

To uses basis set projection and fragment guesses you have to run the smaller basis set calculation with fragments first, and then read this into a second calculation which does the projection

 $molecule
    0 1
 --
 0 1
    H       0.000000    -0.115747     1.133769
    H       0.000000     1.109931    -0.113383
    O       0.000000     0.005817    -0.020386
 --
 0 1
    He      10000   0 0
 $end
 $rem
    JOBTYPE              sp
    EXCHANGE             b3lyp
    BASIS                cc-pVDZ
    scf_guess fragmo
    CORRELATION          none
    SYMMETRY             false
    SYM_IGNORE           true
 $end
 @@@
 $molecule
 read
 $end
 $rem
    scf_guess read
    JOBTYPE              sp
    EXCHANGE             b3lyp
    BASIS                cc-pVTZ
    BASIS2                cc-pVDZ
    CORRELATION          none
    MAX_SCF_CYCLES       600
    SYMMETRY             false
    SYM_IGNORE           true
    basisprojtype ovprojection
 $end

INTDUMP / FCIDUMP

To create files in the FCIDUMP format (used e.g. by Hande) create a QChem input file:

$molecule
0 1
  H 0 0 0
  H 1 0 0
$end

$rem
  correlation idump
  exchange hf
  basis sto-3G
  use_abelian_subgroup true
  scf_guess_print 9999
$end

and use the version of QChem currently (2020-02-20) available from:

[you@liminal] $ export QC=public_o
[you@liminal] $ source ~ajwt3/code/qchem/qcsetup.bash
[you@liminal] $ qchem your-input-file.in

This should produce a file called INTDUMP

 &FCI NORB= 2,NELEC=  2,MS2=  0
  ORBSYM=1,6,
  ISYM=1 UHF=.FALSE.
 &END
     0.62640249948715   1   1   1   1
     0.19679058349422   1   2   1   2
      0.6217067630807   2   2   1   1
     0.19679058349422   2   1   1   2
     0.19679058349422   2   1   2   1
     0.65307074688898   2   2   2   2
     -1.1108441795661   1   1   0   0
    -0.58912100326925   2   2   0   0
    -0.39980670964291   1   0   0   0
     0.37823811728909   2   0   0   0
     0.52917721026434   0   0   0   0