# Sample input files

## Water SCF calculation and geometry optimization in a 6-31g basis

The [Getting Started](Getting-Started) input file performs a
geometry optimization in a single task. A single point SCF energy
calculation is performed and then restarted to perform the optimization
(both could of course be performed in a single task).

### Job 1. Single point SCF energy
```
 start h2o 
 title "Water in 6-31g basis set" 
 
 geometry units au  
   O      0.00000000    0.00000000    0.00000000  
   H      0.00000000    1.43042809   -1.10715266  
   H      0.00000000   -1.43042809   -1.10715266 
 end  
 basis  
   H library 6-31g  
   O library 6-31g  
 end
 task scf
```
The final energy should be -75.983998.

### Job 2. Restarting and perform a geometry optimization
```
 restart h2o
 title "Water geometry optimization"
 
 task scf optimize
```
There is no need to specify anything that has not changed from the
previous input deck, though it will do no harm to repeat it.

## Compute the polarizability of Ne using finite field

### Job 1. Compute the atomic energy
```
 start ne
 title "Neon"
 geometry; ne 0 0 0; end
 basis spherical 
   ne library aug-cc-pvdz
 end
 scf; thresh 1e-10; end
 task scf
```
The final energy should be -128.496350.

### Job 2. Compute the energy with applied field

An external field may be simulated with point charges. The charges here
apply a field of magnitude 0.01 atomic units to the atom at the origin.
Since the basis functions have not been reordered by the additional
centers we can also restart from the previous vectors, which is the
default for a restart job.
```
 restart ne  
 title "Neon in electric field"  
 geometry units atomic  
   bq1 0 0 100 charge 50  
   ne  0 0 0  
   bq2 0 0 -100 charge -50  
 end  
 task scf
```
The final energy should be -128.496441, which together with the previous
field-free result yields an estimate for the polarizability of 1.83
atomic units. Note that by [default](Geometry) NWChem does
not include the interaction between the two point charges in the total
energy.

## SCF energy of H<sub>2</sub>CO using ECPs for C and O

The following will compute the SCF energy for formaldehyde with ECPs on
the Carbon and Oxygen centers.
```
title "formaldehyde ECP deck"  
  
start ecpchho  
  
geometry units au  
  C         0.000000  0.000000 -1.025176  
  O         0.000000  0.000000  1.280289  
  H         0.000000  1.767475 -2.045628  
  H         0.000000 -1.767475 -2.045628  
end  
  
basis   
  C  SP  
   0.1675097360D+02 -0.7812840500D-01  0.3088908800D-01  
   0.2888377460D+01 -0.3741108860D+00  0.2645728130D+00  
   0.6904575040D+00  0.1229059640D+01  0.8225024920D+00  
  C  SP  
   0.1813976910D+00  0.1000000000D+01  0.1000000000D+01  
  C  D  
   0.8000000000D+00  0.1000000000D+01  
  C  F  
   0.1000000000D+01  0.1000000000D+01  
  O  SP  
   0.1842936330D+02 -0.1218775590D+00  0.5975796600D-01  
   0.4047420810D+01 -0.1962142380D+00  0.3267825930D+00  
   0.1093836980D+01  0.1156987900D+01  0.7484058930D+00  
  O  SP  
   0.2906290230D+00  0.1000000000D+01  0.1000000000D+01  
  O  D  
   0.8000000000D+00  0.1000000000D+01  
  O  F  
   0.1100000000D+01  0.1000000000D+01  
  H  S  
   0.1873113696D+02  0.3349460434D-01  
   0.2825394365D+01  0.2347269535D+00  
   0.6401216923D+00  0.8137573262D+00  
  H  S     
   0.1612777588D+00  0.1000000000D+01  
end  
  
ecp  
  C nelec 2  
  C ul  
        1       80.0000000       -1.60000000  
        1       30.0000000       -0.40000000  
        2        0.5498205       -0.03990210  
  C s  
        0        0.7374760        0.63810832  
        0      135.2354832       11.00916230  
        2        8.5605569       20.13797020  
  C p  
        2       10.6863587       -3.24684280  
        2       23.4979897        0.78505765  
  O nelec 2  
  O ul  
        1       80.0000000       -1.60000000  
        1       30.0000000       -0.40000000  
        2        1.0953760       -0.06623814  
  O s  
        0        0.9212952        0.39552179  
        0       28.6481971        2.51654843  
        2        9.3033500       17.04478500  
  O p  
        2       52.3427019       27.97790770  
        2       30.7220233      -16.49630500  
end  
  
scf  
  vectors input hcore  
  maxiter 20  
end  
  
task scf
```
This should produce the following output:
```
      Final RHF  results   
      ------------------   
       
        Total SCF energy =    -22.507927218024  
     One electron energy =    -71.508730162974  
     Two electron energy =     31.201960019808  
Nuclear repulsion energy =     17.798842925142
```
## MP2 optimization and CCSD(T) on nitrogen

The following performs an MP2 geometry optimization followed by a
CCSD(T) energy evaluation at the converged geometry. A Dunning
correlation-consistent triple-zeta basis is used. The default of
Cartesian basis functions must be overridden using the keyword spherical
on the BASIS directive. The 1s core orbitals are frozen in both the MP2
and coupled-cluster calculations (note that these must separately
specified). The final MP2 energy is -109.383276, and the CCSD(T) energy
is -109.399662.
```
start n2   
  
geometry  
  symmetry d2h  
  n 0 0 0.542  
end  
  
basis spherical  
  n library cc-pvtz  
end  
  
mp2  
  freeze core  
end  
  
task mp2 optimize  
  
ccsd  
  freeze core  
end  
  
task ccsd(t)
```