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To investigate this issue , the energy landscapes of pernitrides of metals with different maximum valence ( M = Ca , Sr , Ba , La , and Ti ) were globally explored on the ab initio level at standard and high pressures , thereby yielding possible ( meta ) stable modifications in these systems together with information on how the landscape changed as function of the valence of the metal cation .
 Chemical: pernitrides; Chemical: Ca; Chemical: Sr; Chemical: Ba; Chemical: La; Chemical: Ti
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: pernitrides; Chemical: Ca; Chemical: Sr; Chemical: Ba; Chemical: La; Chemical: Ti