# Quadratic Response Functions
## Available Methods  
- [`CCS`](./../general_sections/jobs.md#CCS)
- [`CCSD`](./../general_sections/jobs.md#CCSD)
- [`CCSDT`](./../general_sections/jobs.md#CCSDT)

## Example Input File
An example using CCS is given below:  
```
@method settings
basis: STO-3G
@end

@memory
max_mem: 1
@end

@jobs
task: ccs
@end

@ccs
restart: False
solver_thresh: 1.0E-12
operators: DIPLEN ANGMOM DIPVEL 
frequency: 0.1
ratio: 2 -1 -1
@end

@scf
conv_thresh: 1.0E-12
@end

@molecule
charge: 0
multiplicity: 1
units: bohr
xyz:
O        0.0000000000    0.0000000000    0.0000000000
H        0.0000000000    1.4304281903    1.1071565216
H        0.0000000000   -1.4304281903    1.1071565216
@end
```

## Relevant Keywords

For keywords, go to [Relevant Keywords](./linearresponse.md#relevant-keywords) in the linear response section.