Add InterfaceCalc Class for Interface Structure and Energy Calculation

src/matcalc/__init__.py

@@ -12,6 +12,7 @@
 from ._base import ChainedCalc, PropCalc
 from ._elasticity import ElasticityCalc
 from ._eos import EOSCalc
+from ._interface import InterfaceCalc
 from ._lammps import LAMMPSMDCalc
 from ._md import MDCalc
 from ._neb import NEBCalc

src/matcalc/_interface.py

@@ -0,0 +1,253 @@
+"""Interface structure/energy calculations."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any
+
+import numpy as np
+from pymatgen.analysis.interfaces.coherent_interfaces import CoherentInterfaceBuilder
+from pymatgen.analysis.structure_matcher import StructureMatcher
+
+from ._base import PropCalc
+from ._relaxation import RelaxCalc
+
+if TYPE_CHECKING:
+    from ase import Atoms
+    from ase.calculators.calculator import Calculator
+    from ase.optimize.optimize import Optimizer
+    from pymatgen.analysis.interfaces.zsl import ZSLGenerator
+    from pymatgen.core import Structure
+
+
+class InterfaceCalc(PropCalc):
+    """
+    This class generates all possible coherent interfaces between two bulk structures
+    given their miller indices, relaxes them, and computes their interfacial energies.
+    """
+
+    def __init__(
+        self,
+        calculator: Calculator | str,
+        *,
+        relax_bulk: bool = True,
+        relax_interface: bool = True,
+        fmax: float = 0.1,
+        optimizer: str | Optimizer = "BFGS",
+        max_steps: int = 500,
+        relax_calc_kwargs: dict | None = None,
+    ) -> None:
+        """Initialize the instance of the class.
+
+        Parameters:
+            calculator (Calculator | str): An ASE calculator object used to perform energy and force
+                calculations. If string is provided, the corresponding universal calculator is loaded.
+            relax_bulk (bool, optional): Whether to relax the bulk structures before interface
+                calculations. Defaults to True.
+            relax_interface (bool, optional): Whether to relax the interface structures. Defaults to True.
+            fmax (float, optional): The maximum force tolerance for convergence. Defaults to 0.1.
+            optimizer (str | Optimizer, optional): The optimization algorithm to use. Defaults to "BFGS".
+            max_steps (int, optional): The maximum number of optimization steps. Defaults to 500.
+            relax_calc_kwargs: Additional keyword arguments passed to the
+            class:`RelaxCalc` constructor for both bulk and interface. Default is None.
+
+        Returns:
+            None
+        """
+        self.calculator = calculator
+        self.relax_bulk = relax_bulk
+        self.relax_interface = relax_interface
+        self.fmax = fmax
+        self.optimizer = optimizer
+        self.max_steps = max_steps
+        self.relax_calc_kwargs = relax_calc_kwargs
+
+    def calc_interfaces(
+        self,
+        film_bulk: Structure,
+        substrate_bulk: Structure,
+        film_miller: tuple[int, int, int],
+        substrate_miller: tuple[int, int, int],
+        zslgen: ZSLGenerator | None = None,
+        cib_kwargs: dict | None = None,
+        **kwargs: Any,
+    ) -> list[dict[str, Any]]:
+        """Calculate all possible coherent interfaces between two bulk structures.
+
+        Parameters:
+            film_bulk (Structure): The bulk structure of the film material.
+            substrate_bulk (Structure): The bulk structure of the substrate material.
+            film_miller (tuple[int, int, int]): The Miller index for the film surface.
+            substrate_miller (tuple[int, int, int]): The Miller index for the substrate surface.
+            zslgen (ZSLGenerator | None, optional): An instance of ZSLGenerator to use for generating
+                supercells.
+            zsl_kwargs (dict | None, optional): Additional keyword arguments to pass to the
+                ZSLGenerator.
+            cib_kwargs (dict | None, optional): Additional keyword arguments to pass to the
+                CoherentInterfaceBuilder.
+            **kwargs (Any): Additional keyword arguments passed to calc_many.
+
+        Returns:
+                dict: A list of dictionaries containing the calculated film, substrate, interface.
+        """
+        cib = CoherentInterfaceBuilder(
+            film_structure=film_bulk,
+            substrate_structure=substrate_bulk,
+            film_miller=film_miller,
+            substrate_miller=substrate_miller,
+            zslgen=zslgen,
+            **(cib_kwargs or {}),
+        )
+
+        terminations = cib.terminations
+        all_interfaces: list = []
+        for t in terminations:
+            interfaces_for_termination = cib.get_interfaces(termination=t)
+            all_interfaces.extend(list(interfaces_for_termination))
+
+        if not all_interfaces:
+            raise ValueError(
+                "No interfaces found with the given parameters. Adjust the ZSL parameters to find more matches."
+            )
+
+        # Group similar / duplicate interfaces using StructureMatcher and keep one representative per group
+        matcher = StructureMatcher()
+        groups: list[list] = []
+        for i in all_interfaces:
+            placed = False
+            for g in groups:
+                if matcher.fit(i, g[0]):
+                    g.append(i)
+                    placed = True
+                    break
+            if not placed:
+                groups.append([i])
+        unique_interfaces = [g[0] for g in groups]
+
+        film_bulk = film_bulk.to_conventional()
+        substrate_bulk = substrate_bulk.to_conventional()
+
+        relaxer_bulk = RelaxCalc(
+            calculator=self.calculator,
+            fmax=self.fmax,
+            max_steps=self.max_steps,
+            relax_cell=self.relax_bulk,
+            relax_atoms=self.relax_bulk,
+            optimizer=self.optimizer,
+            **(self.relax_calc_kwargs or {}),
+        )
+        film_opt = relaxer_bulk.calc(film_bulk)
+        substrate_opt = relaxer_bulk.calc(substrate_bulk)
+
+        interfaces = [
+            {
+                "interface": interface,
+                "num_atoms": len(interface),
+                "film_energy_per_atom": film_opt["energy"] / len(film_bulk),
+                "final_film": film_opt["final_structure"],
+                "substrate_energy_per_atom": substrate_opt["energy"] / len(substrate_bulk),
+                "final_substrate": substrate_opt["final_structure"],
+            }
+            for interface in unique_interfaces
+        ]
+
+        return [r for r in self.calc_many(interfaces, **kwargs) if r is not None]
+
+    def calc(
+        self,
+        structure: Structure | Atoms | dict[str, Any],
+    ) -> dict[str, Any]:
+        """Calculate the interfacial energy of the given interface structures and sort by the energy.
+
+        Parameters:
+            structure : A dictionary containing the film, substrate, interface structures
+
+        Returns:
+            dict:
+                - "interface" (Structure): The initial interface structure.
+                - "final_interface" (Structure): The relaxed interface structure.
+                - "interface_energy_per_atom" (float): The final energy of the relaxed interface structure.
+                - "num_atoms" (int): The number of atoms in the interface structure.
+                - "interfacial_energy" (float): The calculated interfacial energy
+        """
+        if not isinstance(structure, dict):
+            msg = (
+                "For interface calculations, structure must be a dict in one of the following formats: "
+                "{'interface': interface_struct, 'film_energy_per_atom': energy, ...} from calc_interfaces or "
+                "{'interface': interface_struct, 'film_bulk': film_struct, 'substrate_bulk': substrate_struct}."
+            )
+            raise TypeError(msg)
+
+        # Type narrowing: at this point, structure is guaranteed to be dict[str, Any]
+        result_dict = structure.copy()
+
+        if "film_energy_per_atom" in structure and "substrate_energy_per_atom" in structure:
+            film_energy_per_atom = structure["film_energy_per_atom"]
+            substrate_energy_per_atom = structure["substrate_energy_per_atom"]
+            film_structure = structure["final_film"]
+            substrate_structure = structure["final_substrate"]
+        else:
+            relaxer = RelaxCalc(
+                calculator=self.calculator,
+                fmax=self.fmax,
+                max_steps=self.max_steps,
+                relax_cell=self.relax_bulk,
+                relax_atoms=self.relax_bulk,
+                optimizer=self.optimizer,
+                **(self.relax_calc_kwargs or {}),
+            )
+            film_opt = relaxer.calc(structure["film_bulk"])
+            film_energy_per_atom = film_opt["energy"] / len(film_opt["final_structure"])
+            film_structure = film_opt["final_structure"]
+            substrate_opt = relaxer.calc(structure["substrate_bulk"])
+            substrate_energy_per_atom = substrate_opt["energy"] / len(substrate_opt["final_structure"])
+            substrate_structure = substrate_opt["final_structure"]
+
+        interface = structure["interface"]
+        relaxer = RelaxCalc(
+            calculator=self.calculator,
+            fmax=self.fmax,
+            max_steps=self.max_steps,
+            relax_cell=False,
+            relax_atoms=self.relax_interface,
+            optimizer=self.optimizer,
+            **(self.relax_calc_kwargs or {}),
+        )
+        interface_opt = relaxer.calc(interface)
+        final_interface = interface_opt["final_structure"]
+        interface_energy = interface_opt["energy"]
+
+        # pymatgen interface object does not include interface properties for interfacial energy
+        # calculation, define them here
+
+        matrix = interface.lattice.matrix
+        area = float(np.linalg.norm(np.cross(matrix[0], matrix[1])))
+
+        unique_in_film = set(film_structure.symbol_set) - set(substrate_structure.symbol_set)
+        unique_in_substrate = set(substrate_structure.symbol_set) - set(film_structure.symbol_set)
+
+        if unique_in_film:
+            unique_element = next(iter(unique_in_film))
+            count = film_structure.composition[unique_element]
+            film_in_interface = (interface.composition[unique_element] / count) * film_structure.num_sites
+            substrate_in_interface = interface.num_sites - film_in_interface
+        elif unique_in_substrate:
+            unique_element = next(iter(unique_in_substrate))
+            count = substrate_structure.composition[unique_element]
+            substrate_in_interface = (interface.composition[unique_element] / count) * substrate_structure.num_sites
+            film_in_interface = interface.num_sites - substrate_in_interface
+        else:
+            msg = "No unique elements found in either structure to determine atom counts in interface."
+            raise ValueError(msg)
+
+        gamma = (
+            interface_energy
+            - (film_in_interface * film_energy_per_atom + substrate_in_interface * substrate_energy_per_atom)
+        ) / (2 * area)
+
+        return result_dict | {
+            "interface": interface,
+            "final_interface": final_interface,
+            "interface_energy_per_atom": interface_energy / len(interface),
+            "num_atoms": len(interface),
+            "interfacial_energy": gamma,
+        }

tests/conftest.py

@@ -52,6 +52,12 @@ def Si() -> Structure:
     return PymatgenTest.get_structure("Si")
 
 
+@pytest.fixture(scope="session")
+def SiO2() -> Structure:
+    """SiO2 structure as session-scoped fixture."""
+    return PymatgenTest.get_structure("SiO2")
+
+
 @pytest.fixture(scope="session")
 def Si_atoms() -> Atoms:
     """Si atoms as session-scoped fixture."""

tests/test_interface.py

@@ -0,0 +1,46 @@
+"""Tests for the InterfaceCalc class."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import pytest
+
+from matcalc import InterfaceCalc
+
+if TYPE_CHECKING:
+    from matgl.ext.ase import PESCalculator
+    from pymatgen.core import Structure
+
+
+def test_interface_calc_basic(Si: Structure, SiO2: Structure, m3gnet_calculator: PESCalculator) -> None:
+    """
+    Test the basic workflow:
+      1) calc_interfaces on SiO2 (film) and Si (substrate)
+      2) calc on the resulting interfaces
+      3) Check the final results
+    """
+    interface_calc = InterfaceCalc(
+        calculator=m3gnet_calculator,
+        relax_bulk=True,
+        relax_interface=True,
+        fmax=0.1,
+        max_steps=100,
+    )
+
+    results = list(
+        interface_calc.calc_interfaces(
+            film_bulk=SiO2,
+            substrate_bulk=Si,
+            film_miller=(1, 0, 0),
+            substrate_miller=(1, 1, 1),
+        )
+    )
+    interface_res = results[0]
+    assert "final_film" in interface_res
+    assert "final_substrate" in interface_res
+    assert "final_interface" in interface_res
+
+    assert interface_res["film_energy_per_atom"] == pytest.approx(-7.881573994954427, rel=1e-1)
+    assert interface_res["substrate_energy_per_atom"] == pytest.approx(-5.419038772583008, rel=1e-1)
+    assert interface_res["interfacial_energy"] == pytest.approx(0.14220127996544243, rel=1e-1)