Multi-elements systems position and species desync bug when block_tridiagonal = True

[AsymmetryChou]

Describe the bug

This is a severe bug when treating multi-elements devices (such as 'C' and 'H') with 'block_tridiagonal=True'. The current version only sorts the positions of the atoms, leaving atom species not changed. This would triggle wrong transport properties in DPNEGF.

Expected behavior

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To Reproduce

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Environment

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Additional Context

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[AsymmetryChou]

Fix it by #33 .