# Development:Sample

### From NWChem

## Contents |

# Sample input files

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

The 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 NWChem does not include the interaction between the two point charges in the total energy.

## SCF energy of *H*_{2}*C**O* 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)