abacus: fix bug in reading nspin2 results (#758)

fix #757 

<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

- **New Features**
- Enhanced handling of magnetic moments and forces to ensure consistent
three-dimensional vector representation.
- Updated input parameters for calculation configuration to reflect
changes in naming conventions and spin configurations.

- **Tests**
- Introduced a new test method to validate behavior with the updated
input file, improving test coverage and ensuring accuracy in results.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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Co-authored-by: root <pxlxingliang>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

dpdata/abacus/scf.py

@@ -478,14 +478,20 @@ def get_mag_force(outlines):
             j = i + 2
             mag = []
             while "-------------------------" not in outlines[j]:
-                mag.append([float(ii) for ii in outlines[j].split()[1:]])
+                imag = [float(ii) for ii in outlines[j].split()[1:]]
+                if len(imag) == 1:
+                    imag = [0, 0, imag[0]]
+                mag.append(imag)
                 j += 1
             mags.append(mag)
         if "Magnetic force (eV/uB)" in line:
             j = i + 2
             magforce = []
             while "-------------------------" not in outlines[j]:
-                magforce.append([float(ii) for ii in outlines[j].split()[1:]])
+                imagforce = [float(ii) for ii in outlines[j].split()[1:]]
+                if len(imagforce) == 1:
+                    imagforce = [0, 0, imagforce[0]]
+                magforce.append(imagforce)
                 j += 1
             magforces.append(magforce)
     return np.array(mags), np.array(magforces)

tests/abacus.spin/INPUT → tests/abacus.spin/INPUT.scf.nspin2

@@ -1,5 +1,5 @@
 INPUT_PARAMETERS
-suffix	ABACUS
+suffix	ABACUS-nspin2
 calculation	scf
 ecutwfc	100
 scf_thr	1e-07
@@ -14,7 +14,7 @@ basis_type	lcao
 symmetry	0
 noncolin	1
 lspinorb	0
-nspin	4
+nspin	2
 out_mul	true
 sc_mag_switch	1
 decay_grad_switch	1