Liu, H. Hao, J.K. Yang, Z.T. JACoW Publishing Geneva, Switzerland 2673-5504 978-3-95450-234-9 10.18429/JACoW-SRF2023-WEPWB084 English 778-783 niobium lattice electron site cavity Contribution to a conference proceedings 2023 2023-09 https://doi.org/10.18429/JACoW-SRF2023-WEPWB084 https://jacow.org/srf2023/papers/wepwb084.pdf We calculate the interaction among zero dimensional defects in niobium lattice through first-principles calculation. And we compare the trapping effect of hydrogen among carbon, nitrogen, and oxygen as well as the trapping effect of interstitial atoms by vacancy. We find that the interstitial C/N/O have similar effect of trapping interstitial hydrogen in niobium lattice, and the vacancy can trap interstitial C/N/O/H in adjacent protocells and strengthen their chemical bond with Nb. These calculations give some explanation for improving superconducting performance of niobium cavities through medium temperature baking.