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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
   H library 6-31g
   O library 6-31g
 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
 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
 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 H2CO 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

  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

  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

  vectors input hcore
  maxiter 20

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 

  symmetry d2h
  n 0 0 0.542

basis spherical
  n library cc-pvtz

  freeze core

task mp2 optimize

  freeze core

task ccsd(t)