Implementation of the Boys and Bernardi counterpoise correction[1] for basis set superposition error. This interface implements it for the total energy and its derivatives, five calculations are required to isolate the BSSE and remove it. For counterpoise-corrected calculations of interaction energy, use the option bsse_correction in the interaction protocol as it is more efficient (only three calculations are needed).

- Boys, S.; Bernardi, F. Mol. Phys. 1970, 19, 553.

The interface implements a single unnamed method; 'method' keyword not necessary

- calculation - Setup for the calculation

- molecule_a - Block defining monomer A (should contain keywords selection, charge, multiplicity)
- molecule_b - Block defining monomer B (should contain keywords selection, charge, multiplicity)

This interface does not use any specific keywords

The following examples, along with all other files needed to run them, can be found in the directory cuby4/interfaces/counterpoise/examples

```
#===============================================================================
# Counterpoise example 1: energy calculation
#===============================================================================
# Counterpoise-corrected energy calculation
job: energy
interface: counterpoise
# The calculation method has to be specified in a separate block,
# note that the keyword "job" is not present
calculation:
interface: turbomole
method: HF
basisset: SVP
# Water dimer from Cuby's database
geometry: A24:water_dimer
charge: 0
# The energy components list also the uncorrected energy
# and corerc ted and uncorrected interaction energies:
print: energy_decomposition
# The following input is optional in this case as cuby can find the two
# moelcules automatically and in the case of neutral singlet dimer, it assumes
# them to be neutral singlets too
molecule_a:
selection: 1-3
charge: 0
multiplicity: 1
molecule_b:
selection: 4-6
charge: 0
multiplicity: 1
```

```
#===============================================================================
# Counterpoise example 2: geometry optimization
#===============================================================================
# Counterpoise-corrected geometry optimization
job: optimize
interface: counterpoise
# Run three calculations in parallel
cuby_threads: 3
# Higher-quality optimization, the result will be used in vibrational calculation
optimizer: rfo
opt_quality: 0.1
# The calculation method has to be specified in a separate block,
# note that the keyword "job" is not present
calculation:
interface: turbomole
method: HF
basisset: SVP
scf_convergence: 8
# Water dimer from Cuby's database
geometry: A24:water_dimer
charge: 0
```

```
#===============================================================================
# Counterpoise example 3: vibrational frequencies
#===============================================================================
# Counterpoise-corrected harmonic vibrational frequencies
job: frequencies
interface: counterpoise
# Run three calculations in parallel
cuby_threads: 3
# The calculation method has to be specified in a separate block,
# note that the keyword "job" is not present
calculation:
interface: turbomole
density_fitting: none # Turbomole's RI has to be disabled for hessian calculations
method: HF
basisset: SVP
scf_convergence: 8
# Geometry from previous example
geometry: optimized.xyz
charge: 0
```