As each crystal is a distinct chemical entity, we followed a simple criterion to define positive and negative pairs: A crystal and any part of the text describing the geometries of the crystal define a positive pair. On the other hand, the crystal and any part of the text describing the other crystals define negative pairs. Note that, for each crystal, there are multiple positive pairs defined for the local atomic environments, their connections, and the space group. As described in Section 2, randomly sampled sentences were used in each epoch, which allows for our model to learn each concept one by one as well as the contexts by inputting a text with two sentences.