#! /bin/sh

# This example demonstrates how to use different levels of numerical precision
# for different regions, with the aim of increasing computational efficiency.

# Let us assume that we are interested in having an accurate description only
# for a subregion of a large chemical system (in this simple example, the
# central water molecule). The system can be divided into sub-regions and
# different levels of numerical accuracy can be used for each of these sub-
# regions.

# In this example we will tweak:
# - the basis set (Basis)
# - the numerical integration (BeckeGrid)
# - the density fitting for Coulomb potential (ZlmFit)
# - the fit-set used in the Hartree-Fock Resolution of identity (RIHartreeFock)

# Note: For the regions for which no quality has been explicitly defined
# through a QualityPerRegion keyword, the quality defined in NumericalQuality
# will be used (Normal, in this example).

$AMSBIN/ams <<eor

Task SinglePoint

System
  Atoms
     O    0.00000000       0.00000000       0.00000000    region=Accurate
     H    0.40399229      -0.65578342       0.63241539    region=Accurate
     H    0.81410032       0.55624569      -0.23129097    region=Accurate
     O   -3.02535626      -0.08473104      -0.47678489
     H   -2.56531481       0.62644005       0.07759386
     H   -2.25289644      -0.61700366      -0.80790649
     O    2.95394790      -0.54939973      -0.38206034
     H    3.91427727      -0.21304908      -0.44738291
     H    2.87780992      -1.13241278      -1.20853726
     O   -5.95425742      -0.56764616      -0.02016682    region=Far
     H   -5.26308282      -0.46969096       0.69255963    region=Far
     H   -5.42117992      -0.54361203      -0.86443121    region=Far
     O    6.25171470      -0.62004899      -0.03702467    region=Far
     H    6.16508647      -1.38696453       0.58541903    region=Far
     H    7.09161199      -0.16700550       0.23679419    region=Far
  End
End

Engine Band

   XC
      LibXC B3LYP
   End

   ! ========================================================
   ! Set different basis sets for atoms in different regions:
   ! ========================================================

   Basis
      Type DZ
      Core None
      PerRegion Region=Accurate Type=TZP
      PerRegion Region=Far      Type=SZ
   End

   ! =============================================================
   ! Set the NumerialQuality to be used for the atoms that are not
   ! explicitely defined through a QualityPerRegion keyword
   ! =============================================================

   NumericalQuality Normal

   ! ======================
   ! Numerical integration:
   ! ======================

   BeckeGrid
      QualityPerRegion Region=Accurate Quality=Good
      QualityPerRegion Region=Far      Quality=Basic
   End

   ! ======================================
   ! Density fitting for Coulomb potential:
   ! ======================================

   ZlmFit
      QualityPerRegion Region=Accurate Quality=Good
      QualityPerRegion Region=Far      Quality=Basic
   End

   ! ============================================================
   ! Hartree-Fock Resolution of identity (for hybrid functionals)
   ! ============================================================

   RIHartreeFock
      QualityPerRegion Region=Accurate Quality=Good
      QualityPerRegion Region=Far      Quality=Basic
   End

   Relativity Level=None

EndEngine

eor