# stm keywords

STM calculator

## stm.z0

If texttt{stm.z0} is set to \$z_0\$, then the tunneling matrix elements
are computed on the plane \$z = z_0\$ using Eq. ref{eq:bardeenM}.
Moreover, the system is decomposed into orbitals below (sample) and
above (tip) the \$z_0\$-plane. Thence, the PDOS of the sample and tip
(\$n\^S\$ and \$n\^T\$), and the sample and tip wavefunctions
(\$psi\^S\$ and \$psi\^T\$) depend on the value of texttt{stm.z0}.

**type**: `scalar`

**example**: `stm.z0 = 20.3`

## stm.voltage

Bias between the sample and tip.

**type**: `scalar`

**example**: `stm.voltage = -0.1`
