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Metal - pernitride compounds belong to a class of chemical systems in which both the complex ions and the non - bonding electrons may play roles in the formation of their modified crystalline structures .
 Chemical: Metal - pernitride
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Metal - pernitride