Spells like like Booming Blade and Green-Flame Blade has secondary damage effects.
Booming Blade deals an extra 1d8 thunder damage if the creature hit with the spell's initial melee attack requirement moves 5 or more feet
Green-Flame blade does a Caster's Spellcasting Ability modifier in radiant damage to a target within 5 feet of the cantrip's original target. This damage incerease by 1d8+ at specific levels
These extra damage stems from attack roll and does have a damage die/dice. Do these extra damage dice also double from a critical hit
Ex: Booming Blade (at base) with a rapier would do 4d8 (2d8 weapon crit + 2d8 thunder spell crit ) on a critical and if the target moves 5+ feet it takes 1d8 thunder damage or does it take 2d8
Green-Flame Blade (at 5th Lv PC) with a rapier 4d8 (2d8 weapon crit + 2d8 radiant spell crit ) on a critical and an adjacent creature within 5 feet of the target gets an additional 1d8 + Spellcasting Ability modifier radiant damage or does it take 2d8 + SAM