add RL colab link

Author: zdcao121

README.md

@@ -62,8 +62,9 @@ Major milestones are summarized below.
 
 **Notebooks**: The quickest way to get started with _CrystalFormer_ is our notebooks in the Google Colab and Bohrium (Chinese version) platforms:
 
-- CrystalFormer Quickstart [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/drive/1IMQV6OQgIGORE8FmSTmZuC5KgQwGCnDx?usp=sharing) [![Open In Bohrium](https://cdn.dp.tech/bohrium/web/static/images/open-in-bohrium.svg)](https://nb.bohrium.dp.tech/detail/68177247598): GUI notebook demonstrating the conditional generation of crystalline materials with _CrystalFormer_;
-- CrystalFormer Application [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/drive/1QdkELaQXAHR1zEu2fcdfgabuoP61_wbU?usp=sharing): Generating stable crystals with a given structure prototype. This workflow can be applied to tasks that are dominated by element substitution.
+- CrystalFormer Quickstart [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/drive/1IMQV6OQgIGORE8FmSTmZuC5KgQwGCnDx?usp=sharing) [![Open In Bohrium](https://cdn.dp.tech/bohrium/web/static/images/open-in-bohrium.svg)](https://nb.bohrium.dp.tech/detail/68177247598): GUI notebook demonstrating the conditional generation of crystalline materials with _CrystalFormer_
+- CrystalFormer Application [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/drive/1QdkELaQXAHR1zEu2fcdfgabuoP61_wbU?usp=sharing): Generating stable crystals with a given structure prototype. This workflow can be applied to tasks that are dominated by element substitution
+- CrystalFormer-RL [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/drive/1ojSqMQzdnlWZRPOQP20nTvvIh67HXdwp#scrollTo=lKOZgUczOAxE): Reinforcement fine-tuning for materials design
 
 ## Installation