Add docs for lattice constants

Author: ElliottKasoar

docs/source/user_guide/benchmarks/bulk_crystal.rst

@@ -0,0 +1,59 @@
+============
+Bulk Crystal
+============
+
+Lattice constants
+=================
+
+Summary
+-------
+
+Performance in evaluating lattice constants for 23 solids, including pure elements,
+binary compounds, and semiconductors.
+
+
+Metrics
+-------
+
+1. MAE (Experimental)
+
+Mean lattice constant error compared to experimental data
+
+For each formula, a bulk crystal is built using the experimental lattice constants and
+lattice type for the initial structure. This structure is optimised for each model
+using the LBFGS optimiser, with the FrechetCellFilter applied to allow optimisation of
+the cell, until the largest absolute Cartesian component of any interatomic force is
+less than 0.03 eV/Å. The lattice constants of this optimised structure are then
+compared to experimental values.
+
+
+2. MAE (PBE)
+
+Mean lattice constant error compared to PBE data
+
+Same as (1), but optimised lattice constants are compared to reference PBE data.
+
+
+Computational cost
+------------------
+
+Low: tests are likely to less than a minute to run on CPU.
+
+Data availability
+-----------------
+
+Input structures:
+
+* Built from experimental lattice constants from various sources
+
+Reference data:
+
+* Experimental data same as input data
+
+* DFT data
+
+  * Batatia, I., Benner, P., Chiang, Y., Elena, A.M., Kovács, D.P., Riebesell, J.,
+    Advincula, X.R., Asta, M., Avaylon, M., Baldwin, W.J. and Berger, F., 2025. A
+    foundation model for atomistic materials chemistry. The Journal of Chemical
+    Physics, 163(18).
+  * PBE-D3(BJ)

docs/source/user_guide/benchmarks/index.rst

@@ -11,3 +11,4 @@ Benchmarks
     physicality
     molecular_crystal
     molecular
+    bulk_crystal