Penn State reeled off a 17-4 run to break a 23-all tie late in the first half and never looked back.
The Terrapins trailed in the fourth quarter, but avoided becoming the Lady Lions' first top five win since 2004 by holding Penn State scoreless in the final nine minutes and finishing on an 18-0 run.
Talvitie's goal helped Finland win its first game of the World Junior Championship.
In addition to Barratt, freshman Aarne Talvitie scored in his World Junior debut against Finland.
Talvitie is the first Nittany Lion to captain his country at the World Junior Championship.
Barratt will be the first player in Penn State hockey history to play for the United States at the World Junior Championship.