# Arbitrary floating-point types

Since DFTK is completely generic in the floating-point type in its routines, there is no reason to perform the computation using double-precision arithmetic (i.e.`Float64`

). Other floating-point types such as `Float32`

(single precision) are readily supported as well. On top of that we already reported^{[HLC2020]} calculations in DFTK using elevated precision from DoubleFloats.jl or interval arithmetic using IntervalArithmetic.jl. In this example, however, we will concentrate on single-precision computations with `Float32`

. The setup of such a reduced-precision calculation is basically identical to the regular case, since Julia automatically compiles all routines of DFTK at the precision, which is used for the lattice vectors. Apart from setting up the model with an explicit cast of the lattice vectors to `Float32`

, there is thus no change in user code required:

```
using DFTK
# Setup silicon lattice
a = 10.263141334305942 # lattice constant in Bohr
lattice = a / 2 .* [[0 1 1.]; [1 0 1.]; [1 1 0.]]
Si = ElementPsp(:Si, psp=load_psp(:Si, functional="lda"))
atoms = [Si => [ones(3)/8, -ones(3)/8]]
# Cast to Float32, setup model and basis
model = model_DFT(Array{Float32}(lattice), atoms, [:lda_x, :lda_c_vwn])
Ecut = 7
basis = PlaneWaveBasis(model, Ecut, kgrid=[4, 4, 4])
# Run the SCF
scfres = self_consistent_field(basis, tol=1e-4);
```

n Energy Eₙ-Eₙ₋₁ ρout-ρin Diag --- --------------- --------- -------- ---- 1 -7.907597541809 NaN 1.95e-01 4.1 2 -7.912191390991 -4.59e-03 2.99e-02 1.0 3 -7.912386417389 -1.95e-04 2.99e-03 1.2 4 -7.912419319153 -3.29e-05 1.34e-03 2.4

To check the calculation has really run in Float32, we check the energies and density are expressed in this floating-point type:

`scfres.energies`

Energy breakdown: Kinetic 3.0792325 AtomicLocal -2.1794953 AtomicNonlocal 1.7332034 Ewald -8.3978930 PspCorrection -0.2946220 Hartree 0.5415103 Xc -2.3943551 total -7.912419319153

`eltype(scfres.energies.total)`

Float32

`eltype(scfres.ρ.real)`

Float32

- HLC2020M. F. Herbst, A. Levitt, E. Cancès.
*A posteriori error estimation for the non-self-consistent Kohn-Sham equations*ArXiv 2004.13549