Examples By Research Question

The bundled structures are teaching cases. Each example follows the same pattern: question, command, key result, interpretation, and limitation.

Use example_path(...) in Python so examples work after package installation:

from findspingroup import example_path

path = example_path("0.800_MnTe.mcif")

Is MnTe Classified As An Altermagnet?

Question

What are the OSSG/MSG of the supplied collinear MnTe order, and does its nonrelativistic symmetry permit momentum-dependent spin splitting?

Python

from findspingroup import example_path, find_spin_group_basic

result = find_spin_group_basic(example_path("0.800_MnTe.mcif"))

print(result["index"])
print(result["conf"], result["magnetic_phase"])
print(result["msg_bns_number"], result["msg_symbol"])
print(result["properties"])

Key result

194.164.1.1.L
Collinear AFM(Altermagnet)
63.457 Cmcm
ss_wo_soc = k-dependent

Interpretation

The supplied order is collinear and AFM-like under the classifier, with symmetry-allowed momentum-dependent splitting without SOC. That combination produces the (Altermagnet) tag.

Limitation

This does not calculate the band splitting, Néel temperature, domain state, or energetic stability of the supplied order.

What Does “AHC Allowed” Mean For Ferromagnetic Fe?

Question

Does the SOC-compatible symmetry allow anomalous Hall conductivity?

Python

from findspingroup import example_path, find_spin_group_basic

result = find_spin_group_basic(example_path("Fe.mcif"))
print(result["conf"], result["magnetic_phase"])
print(result["properties"]["ahc_w_soc"])
print(result["properties"]["ss_wo_soc"])

Key result

Collinear FM/FiM
AHC with SOC: Yes
spin splitting without SOC: Zeeman

Interpretation

The symmetry does not force the SOC anomalous Hall response to vanish. The FM-like order also permits a momentum-independent exchange/Zeeman-like splitting in the no-SOC classification.

Limitation

Yes is not a conductivity calculation. The magnitude and sign require electronic-structure/Berry-curvature information.

Coplanar Mn3Sn: Moment Geometry Versus Phase

Question

Can a nearly compensated noncollinear antiferromagnet be distinguished from a collinear altermagnet, and what changes with SOC?

Python

from findspingroup import example_path, find_spin_group_basic

result = find_spin_group_basic(example_path("0.200_Mn3Sn.mcif"))

print(result["conf"])
print(result["magnetic_phase"])
print(result["net_moment"])
print(result["properties"])

Key result

Coplanar
AFM (SOM)
net moment approximately 0 μB
AHC with SOC: Yes

Interpretation

Coplanar describes the rank/geometry of the moment directions; AFM (SOM) is the separate symmetry classifier result. SOC-compatible symmetry permits AHC even though the analyzed net moment is numerically zero.

Limitation

The zero-net-moment decision depends on mtol, and symmetry permission does not specify which experimental domain is populated.

Quasi-2D Spin Splitting In V2Te2O

Question

What spin-splitting constraint remains when the supplied structure is interpreted as a layer normal to input axis c?

Python

from findspingroup import example_path, find_spin_group

result = find_spin_group(
    example_path("V2Te2O_input.mcif"),
    calculation_mode="quasi2d",
    vacuum_axis="c",
)

print(result.index)
print(result.quasi_2d["status"])
print(result.quasi_2d["interpretation"])
print(result.quasi_2d["spin_splitting_2d"])

Key result

123.47.1.1.L
interpretation = in_plane_k_dependent
spin_splitting_2d = spin splitting

Interpretation

The quasi-2D path recomputes the allowed in-plane behavior in the two remaining momentum variables and reports momentum-dependent in-plane splitting.

Limitation

The workflow can regularize/extend insufficient vacuum along the selected axis. Inspect geometry, vacuum_axis_input, and reciprocal-transform diagnostics; do not treat quasi-2D output as a simple filter on an unchanged 3D cell.

Export Matched VASP Inputs

Question

How do I obtain a POSCAR and KPOINTS that use the same symmetry setting?

CLI

fsg structure.mcif --write-poscar-kpoints calculation_inputs

Result

calculation_inputs/POSCAR
calculation_inputs/KPOINTS

Both use the ACC primitive real-space setting. Keep them paired. Existing files with those names are replaced.