Why did Edgar Allan Poe use the rhyme scheme abcbbb in the poem The Raven?

Poe likely chose the rhyme scheme abcbbb to create a sense of unease and tension in "The Raven." The repetitive b sound in the sixth line of each stanza adds to the poem's haunting atmosphere and contributes to the overall sense of foreboding. The rhyme scheme also helps to maintain the poem's rhythm and pacing.