Introductory examples

This section explains some very simple calculations in order to help the new user to understand how easy things can be.

Perform a simple SCF calculation for molecular hydrogen. The input is typed in directly and the output is sent to the terminal:

        molpro <<!
        basis=vdz;
        geometry={angstrom;h1;h2,h1,.74}
        hf
        !

The same calculation, with the data taken from the file h2.inp. The output is sent to h2.out. On completion, the file h2.pun is returned to the current directory and the file h2.wf to the directory $HOME/wfu (this is the default):

        molpro h2.inp

h2.inp contains:

examples/h2.inp

        ***,H2
        file,2,h2.wf,new;
        punch,h2.pun;
        basis=vdz;
        geometry={angstrom;h1;h2,h1,.74}
        hf

As before, but the file h2.wf is sent to the directory /tmp/wfu:

molpro -W /tmp/wfu h2.inp

The first example does an SCF calculation for H$_2$O, using all possible defaults.

examples/h2o_scf.inp

***,h2o                   !A title
r=1.85,theta=104          !set geometry parameters
geometry={O;              !z-matrix geometry input
          H1,O,r;
          H2,O,r,H1,theta}
hf                        !closed-shell scf

In the above example, the default basis set (VDZ) is used. We can modify the default basis using a BASIS directive as you can see in the modified example shown in default basis sets.

Now we can also do a geometry optimization, simply by adding the card OPTG.

examples/h2o_scfopt_631g.inp

***,h2o                   !A title
r=1.85,theta=104          !set geometry parameters
geometry={O;              !z-matrix geometry input
          H1,O,r;
          H2,O,r,H1,theta}
basis=6-31g**             !use Pople basis set
hf                        !closed-shell scf
optg                      !do scf geometry optimization

The following job does a CCSD(T) calculation using a larger (VTZ) basis (this includes an $f$ function on oxygen and a $d$ function on the hydrogens).

examples/h2o_ccsdt_vtz.inp

***,h2o                   !A title
r=1.85,theta=104          !set geometry parameters
geometry={O;              !z-matrix geometry input
          H1,O,r;
          H2,O,r,H1,theta}
basis=VTZ                 !use VTZ basis
hf                        !closed-shell scf
ccsd(t)                   !do ccsd(t) calculation

Alternatively, the input could be written as

***,h2o                   !A title
r=1.85,theta=104          !set geometry parameters
geometry={O;              !z-matrix geometry input
          H1,O,r;
          H2,O,r,H1,theta}

run ccsd(t) basis=vtz

or, even shorter:

r=1.85,theta=104          !set geometry parameters
run ccsd(t) basis=vtz geometry={O;H1,O,r;H2,O,r,H1,theta}

In these cases the Hartree-Fock calculation (hf) is implied by the run command.

Perhaps you want to do a CASSCF and subsequent MRCI for comparison. The following uses the full valence active space in the CASSCF and MRCI reference function.

examples/h2o_mrci_vtz.inp

***,h2o                   !A title
r=1.85,theta=104          !set geometry parameters
geometry={o;              !z-matrix geometry input
          h1,O,r;
          h2,O,r,H1,theta}
basis=vtz                 !use VTZ basis
hf                        !closed-shell scf
ccsd(t)                   !do ccsd(t) calculation
casscf                    !do casscf calculation
mrci                      !do mrci calculation

It is possible to use the RUN command to execute single programs. In this case the input can be written in a single line. For more details and examples see Simplified Input.

You may now want to print a summary of all results in a table. To do so, you must store the computed energies in variables:

examples/h2o_table.inp

***,h2o                   !A title
r=1.85,theta=104          !set geometry parameters
geometry={o;              !z-matrix geometry input
          h1,O,r;
          h2,O,r,H1,theta}
basis=vtz                 !use VTZ basis
hf                        !closed-shell scf
e(1)=energy               !save scf energy in variable e(1)
method(1)=program         !save the string 'HF' in variable method(1)

ccsd(t)                   !do ccsd(t) calculation
e(2)=energy               !save ccsd(t) energy in variable e(2)
method(2)=program         !save the string 'CCSD(T)' in variable method(2)

casscf                    !do casscf calculation
e(3)=energy               !save scf energy in variable e(3)
method(3)=program         !save the string 'CASSCF' in variable method(3)
mrci                      !do mrci calculation
e(4)=energy               !save scf energy in variable e(4)
method(4)=program         !save the string 'MRCI' in variable method(4)

table,method,e            !print a table with results
title,Results for H2O, basis=$basis  !title for the table

examples/h2o_tab.inp

***,h2o scf (C2v)
file,1,h2o.int,new
file,2,h2o.wfu,new

theta=104                 !set geometry parameters
basis={                   !define  basis
sp,o,dz;c;d,o,1d          !DZP basis for O
s,h,dz;c;p,h,1p           !DZP basis for H
}

symmetry,x,y
geometry={
o
h,,1.4,,r(i)
h,,-1.4,,r(i)}
r=[1.85,1.90]

do i=1,#r
{hf;occ,3,1,1;             !closed-shell scf
expec,qm}
e(i)=energy
de(i)=(e(i)-e(1))*tokcal
dip(i)=dmz(1)
quadx(i)=qmxx(1)
quady(i)=qmyy(1)
quadz(i)=qmzz(1)
enddo

{table,e,dip,quadx,quady,quadz,de
save,h2o.tab
title,Using defaults
head,energy,'dipole moment','quadrupole z'
}

{table,e,dip,quadx,quady,quadz,de
save,h2o.tab
ftyp,f,d,f,d,f,f
digits,8,4,4,4,4,2
title,Using ftyp=f,d,f,d,f,f and digits=8,4,4,4,4,2
head,energy,'dipole moment','quadrupole z'
}

{table,e,dip,quadx,quady,quadz,de
save,h2o.tab
format,(5x,f14.8,f10.4,2x,f9.4,2x,2f12.3,5x,f9.2)
title,Using explicit format=(5x,f14.8,f10.4,2x,f9.4,2x,2f12.3,5x,f9.2)
head,energy,'dipole moment','quadrupole z'
}
---

This job produces the following table:

 Results for H2O, basis=VTZ

 METHOD        E
 HF        -76.05480122
 CCSD(T)   -76.33149220
 CASSCF    -76.11006259
 MRCI      -76.31960943

You could simplify this job by defining a procedure SAVE_E as follows:

examples/h2o_proce.inp

***,h2o                   !A title

proc save_e               !define procedure save_e
if(#i.eq.0) i=0           !initialize variable i if it does not exist
i=i+1                     !increment i
e(i)=energy               !save scf energy in variable e(i)
method(i)=program         !save the present method in variable method(i)
endproc                   !end of procedure


r=1.85,theta=104          !set geometry parameters
geometry={o;              !z-matrix geometry input
          h1,O,r;
          h2,O,r,H1,theta}
basis=vtz                 !use VTZ basis
hf                        !closed-shell scf
save_e                    !call procedure, save results

ccsd(t)                   !do ccsd(t) calculation
save_e                    !call procedure, save results

casscf                    !do casscf calculation
save_e                    !call procedure, save results

mrci                      !do mrci calculation
save_e                    !call procedure, save results

table,method,e            !print a table with results
title,Results for H2O, basis=$basis  !title for the table

The job produces the same table as before.

For more details about procedures and further examples see Procedures section of Program control.

Now you have the idea that one geometry is not enough. Why not compute the whole surface? DO loops make it easy. Here is an example, which computes a whole potential energy surface for $\rm H_2O$.

examples/h2o_pes_ccsdt.inp

***,H2O potential
symmetry,x                           !use cs symmetry
geometry={
         o;                          !z-matrix
         h1,o,r1(i);
         h2,o,r2(i),h1,theta(i) }
basis=vdz                             !define basis set
angles=[100,104,110]                  !list of angles
distances=[1.6,1.7,1.8,1.9,2.0]       !list of distances
i=0                                   !initialize a counter
do ith=1,#angles                      !loop over all angles H1-O-H2
do ir1=1,#distances                   !loop over distances for O-H1
do ir2=1,ir1                          !loop over O-H2 distances(r1.ge.r2)
i=i+1                                 !increment counter
r1(i)=distances(ir1)                  !save r1 for this geometry
r2(i)=distances(ir2)                  !save r2 for this geometry
theta(i)=angles(ith)                  !save theta for this geometry
hf;                                   !do SCF calculation
escf(i)=energy                        !save scf energy for this geometry
ccsd(t);                              !do CCSD(T) calculation
eccsd(i)=energc                       !save CCSD energy
eccsdt(i)=energy                      !save CCSD(T) energy
enddo                                 !end of do loop ith
enddo                                 !end of do loop ir1
enddo                                 !end of do loop ir2
{table,r1,r2,theta,escf,eccsd,eccsdt   !produce a table with results
head, r1,r2,theta,scf,ccsd,ccsd(t)    !modify column headers for table
save,h2o.tab                          !save the table in file h2o.tab
title,Results for H2O, basis $basis   !title for table
sort,3,1,2}                           !sort table

This produces the following table.

 Results for H2O, basis VDZ

     R1    R2   THETA       SCF            CCSD           CCSD(T)
    1.6   1.6   100.0   -75.99757338   -76.20140563   -76.20403920
    1.7   1.6   100.0   -76.00908379   -76.21474489   -76.21747582
    1.7   1.7   100.0   -76.02060127   -76.22812261   -76.23095473
    ...
    2.0   1.9   110.0   -76.01128923   -76.22745359   -76.23081968
    2.0   2.0   110.0   -76.00369171   -76.22185092   -76.22537212

You can use also use DO loops to repeat your input for different methods.

examples/h2o_manymethods.inp

***,h2o benchmark
$method=[hf,fci,ci,cepa(0),cepa(1),cepa(2),cepa(3),mp2,mp3,mp4,\
      qci,ccsd,bccd,qci(t),ccsd(t),bccd(t),casscf,mrci,acpf]
basis=dz                                !Double zeta basis set
geometry={o;h1,o,r;h2,o,r,h1,theta}     !Z-matrix for geometry
r=1 ang, theta=104                      !Geometry parameters
do i=1,#method                          !Loop over all requested methods
$method(i);                             !call program
e(i)=energy                             !save energy for this method
enddo
escf=e(1)                               !scf energy
efci=e(2)                               !fci energy
table,method,e,e-escf,e-efci            !print a table with results
!Title for table:
title,Results for H2O, basis $basis, R=$r Ang, Theta=$theta degree

This calculation produces the following table.

 Results for H2O, basis DZ, R=1 Ang, Theta=104 degree

 METHOD        E             E-ESCF       E-EFCI
 HF        -75.99897339     .00000000    .13712077
 FCI       -76.13609416    -.13712077    .00000000
 CI        -76.12844693    -.12947355    .00764722
 CEPA(0)   -76.13490643    -.13593304    .00118773
 CEPA(1)   -76.13304720    -.13407381    .00304696
 CEPA(2)   -76.13431548    -.13534209    .00177868
 CEPA(3)   -76.13179688    -.13282349    .00429728
 MP2       -76.12767140    -.12869801    .00842276
 MP3       -76.12839400    -.12942062    .00770015
 MP4       -76.13487266    -.13589927    .00122149
 QCI       -76.13461684    -.13564345    .00147732
 CCSD      -76.13431854    -.13534515    .00177561
 BCCD      -76.13410586    -.13513247    .00198830
 QCI(T)    -76.13555640    -.13658301    .00053776
 CCSD(T)   -76.13546225    -.13648886    .00063191
 BCCD(T)   -76.13546100    -.13648762    .00063315
 CASSCF    -76.05876129    -.05978790    .07733286
 MRCI      -76.13311835    -.13414496    .00297580
 ACPF      -76.13463018    -.13565679    .00146398

One can do even more fancy things, like, for instance, using macros, stored as string variables, see Macro definitions using string variables.