# What is this unit of force?

1. Aug 4, 2015

### Richie9384

I'm reading a paper on a simulation of graphene and carbon nanotube growth on SiC, in the paper they give a few computational details about the structural optimization of the SiC model using a conjugate gradient method and they state the maximal force component as
$$1x10^{-4}Ha/a_o$$

What is this unit? I'm assuming Ha per angstrom...but Ha seem to be a unit of area...I need to convert to eV/Angstrom

2. Aug 4, 2015

### e.bar.goum

I would have guessed that
Ha = Hartree https://en.wikipedia.org/wiki/Hartree
$a_0$ = Bohr radius.

And that gives you energy per unit length, which is what you need.

(ETA: If it were lowercase "ha" would be "hectare" -- if that's what you were thinking. Angstrom is written like Å not $a_0$)

3. Aug 4, 2015

### MrAnchovy

When I bought carpet for my house it came on a roll that covered 5 x 10-14 hectares per Ångstrom