I created an (unscaled, ideal) hcp lattice: `hcp = mg.Lattice([[1,0,0],[1/2,math.sqrt(3)/2,0],[0,0,math.sqrt(8/3)]])`

but I’d like to scale the whole thing by the `a`

lattice parameter. What’s the expected way to do this in `pymatgen`

?

Or maybe the lattice constant should be added when using the defined `Lattice`

when calling `Structure`

?

` hcpZr = mg.Structure(hcp,["Zr","Zr"],[[0,0,0],[1/3,1/3,1/2]])`

(If so, where does one specify the lattice parameter?)

Hi @glwhart,

You specify the lattice constants in the lattice and there is a useful function generating a lattice from the lattice parameters for you:

```
from pymatgen import Lattice, Structure
a = 3#first hcp lattice parameter
c = 7#second hcp lattice parameter
hcp = Lattice.from_parameters(a, a, c, 90, 90, 120)#parameters: a, b, c, alpha, beta, gamma
hcpZr = Structure(hcp, ["Zr","Zr"],[[0,0,0],[1/3,1/3,1/2]])#these are fractional coordinates
```

Best,

Peter

Perfect! That’s exactly the kind of feedback that I was hoping for. Thanks Peter.

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