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introductory_examples [2020/07/13 07:35] – wernerintroductory_examples [2025/10/14 07:46] (current) – [CCSD(T)] werner
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 +====== Introductory examples ======
 +
 +This section explains some very simple calculations in order to help the new user to understand how easy things can be.
 +
 +===== Using the molpro command =====
 +
 +
 +Perform a simple SCF calculation for molecular hydrogen. The input is typed in directly and the output is sent to the terminal:
 +<code>
 +        molpro <<!
 +        basis=vdz;
 +        geometry={angstrom;h1;h2,h1,.74}
 +        hf
 +        !
 +</code>
 +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 ''%%$HOME/wfu%%'' (this is the default):
 +<code>
 +        molpro h2.inp
 +</code>
 +h2.inp contains:
 +<code - examples/h2.inp>
 +        ***,H2
 +        file,2,h2.wf,new;
 +        punch,h2.pun;
 +        basis=vdz;
 +        geometry={angstrom;h1;h2,h1,.74}
 +        hf
 +</code>
 +As before, but the file ''h2.wf'' is sent to the directory ''%%/tmp/wfu%%'':
 +<code>
 +molpro -W /tmp/wfu h2.inp
 +</code>
 +
 +===== Simple SCF calculations =====
 +
 +The first example does an SCF calculation for H$_2$O, using all possible defaults.
 +
 +<code - 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
 +</code>
 +
 +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 [[
 +basis_input#default_basis_sets|default basis sets]].
 +===== Geometry optimizations =====
 +
 +Now we can also do a geometry optimization, simply by adding the card ''OPTG''.
 +
 +<code - 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
 +</code>
 +
 +===== CCSD(T) =====
 +
 +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).
 +
 +<code - 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
 +</code>
 +
 +Alternatively, the input could be written as
 +
 +<code>
 +***,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
 +</code>
 +
 +or, even shorter:
 +
 +<code>
 +r=1.85,theta=104          !set geometry parameters
 +run ccsd(t) basis=vtz geometry={O;H1,O,r;H2,O,r,H1,theta}
 +</code>
 +
 +In these cases the Hartree-Fock calculation (hf) is implied by the ''run'' command. For more details and examples see [[Quickstart|Simple Input]].
 +===== CASSCF and MRCI =====
 +
 +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.
 +
 +<code - 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
 +</code>
 +
 +===== Simplified input =====
 +
 +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 [[Quickstart|Simple Input]].
 +===== Tables =====
 +
 +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:
 +
 +<code - 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
 +</code>
 +
 +<code - 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'
 +}
 +---
 +</code>
 +
 +This job produces the following table:
 +
 +<code>
 + Results for H2O, basis=VTZ
 +
 + METHOD        E
 + HF        -76.05480122
 + CCSD(T)   -76.33149220
 + CASSCF    -76.11006259
 + MRCI      -76.31960943
 +</code>
 +===== Procedures =====
 +
 +You could simplify this job by defining a procedure ''SAVE_E'' as follows:
 +
 +<code - 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
 +</code>
 +
 +The job produces the same table as before.
 +
 +For more details about procedures and further examples see [[program_control#procedures_proc_endproc|Procedures section of Program control]].
 +
 +===== Do loops =====
 +
 +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 $\rm H_2O$.
 +
 +<code - 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 $basis   !title for table
 +sort,3,1,2}                           !sort table
 +</code>
 +
 +This produces the following table.
 +
 +<code>
 + Results for H2O, basis VDZ
 +
 +     R1    R2   THETA       SCF            CCSD           CCSD(T)
 +    1.6   1.6   100.0   -75.99757338   -76.20140563   -76.20403920
 +    1.7   1.6   100.0   -76.00908379   -76.21474489   -76.21747582
 +    1.7   1.7   100.0   -76.02060127   -76.22812261   -76.23095473
 +    ...
 +    2.0   1.9   110.0   -76.01128923   -76.22745359   -76.23081968
 +    2.0   2.0   110.0   -76.00369171   -76.22185092   -76.22537212
 +</code>
 +You can use also use ''DO'' loops to repeat your input for different methods.
 +
 +<code - examples/h2o_manymethods.inp>
 +***,h2o benchmark
 +$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
 +</code>
 +
 +This calculation produces the following table.
 +
 +<code>
 + 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
 +</code>
 +One can do even more fancy things, like, for instance, using macros, stored as string variables, see [[variables#macro_definitions_using_string_variables|Macro definitions using string variables]].