Lattice.md ctd

devtools/architecture/Lattice.md

@@ -7,6 +7,15 @@ Typical sample construction with a 3d lattice:
     iff = ba.InterferenceFunction3DLattice(lattice)
     iff.setPositionVariance(1.)
     iff.setPeakShape(peak_shape)
+
+    layout = ba.ParticleLayout()
+    layout.addParticle(particle)
+    layout.setTotalParticleSurfaceDensity(.01)
+    layout.setInterferenceFunction(iff)
+    layout.setWeight(1.0)
+
+    vacuum_layer = ba.Layer(m_vacuum)
+    vacuum_layer.addLayout(layout)
 ```
 
 `bake::FCCLattice` returns a `Lattice3d` with an fcc primitive cell.