Horford struck for 22 points and hauled down 11 rebounds to pace Atlanta, which broke a close game open with a big fourth quarter.
Smith accounted for 21 points, seven boards and five assists as the Hawks continued their recovery from a stretch that saw them lose six times over a seven-game span.
The Nets, meanwhile, fell for just the second time in six outings despite 18 points from former Hawk Joe Johnson.
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