This has been discussed on the docs list, Diagrama is much more general.
"Assumption" "Suposição"
"Axiom" "Axioma"
"Case" "Caso"
- "Chart" "Diagrama"
+ "Chart" "Gráfico"
"Claim" "Afirmação"
"Conclusion" "Conclusão"
"Condition" "Condição"
"Graph[[mathematical]]" "Grafo"
"Lemma" "Lema"
"List of Algorithms" "Lista de Algoritmos"
- "List of Charts" "Lista de Diagramas"
+ "List of Charts" "Lista de Gráficos"
"List of Graphs[[mathematical]]" "Lista de Grafos"
"List of Schemes" "Lista de Esquemas"
"List of Tableaux" "Lista de Tableaux"
#: lib/layouts/achemso.layout:186
msgid "Chart"
-msgstr "Diagrama"
+msgstr "Gráfico"
#: lib/layouts/achemso.layout:192
msgid "List of Charts"
-msgstr "Lista de Diagramas"
+msgstr "Lista de Gráficos"
#: lib/layouts/achemso.layout:210
msgid "Graph[[mathematical]]"