D infinity h symmetry
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For the isolated molecule such as CO2 which is D infinity h, what is the symmetry group? I could not find this one in the manual
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Hi Jonas,
CRYSTAL does not implement point groups with infinite-order rotations, so \(D_{\infty h}\) cannot be used directly. For linear molecules like CO₂, the practical approach is to approximate the symmetry using a finite-order rotation group.
In this case, \(D_{4h}\) (i.e., 24) is a good option in CRYSTAL. It preserves the key degeneracies of linear molecules, including the doubly degenerate bending modes of CO₂. Using a lower-symmetry group like \(D_{2h}\) would artificially lift these degeneracies.
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Davide, a follow up question. Will that not affect the resulting thermodynamics? I mean translational or rotational (I can never remember) thermodynamics is dependent on symmetry and I am calculating thermodynamic quantities here
