Serena Williams defeated Germany's Tatjana Maria in straight sets to enter the second round at Australian Open.
Roger Federer and Novak Djokovic are both gunning for a record seventh Australian Open crown.
Simona Halep takes the top seeding among the women courtesy of her world number one ranking.
To win the decisive tie-break, a player will need to be the first to 10 with an advantage of at least two points.
Roger Federer will be aiming for a third successive Australian Open.
Roger Federer became the first player to win three Hopman Cups, teaming with Belinda Bencic for the duo's second consecutive title.
World number two Angelique Kerber was too good for the 15th-ranked Barty in the opening match, winning 6-4, 6-4.
Alexander Zverev faltered just once when Novak Djokovic broke him early in the second set but that was the only blemish on an extraordinary performance.
Some fans booed the Alexander Zverev after his superb victory over Roger Federer in the last four of the ATP Finals.
Novak Djokovic is eyeing a record-equalling sixth end-of-season title at London's O2 Arena.
Alexander Zverev, who has three Masters series titles, is the youngest finalist at the event since Juan Martin del Potro in 2009.
Novak Djokovic has enjoyed a remarkable renaissance in the second half of the season after an elbow surgery.
Alexander Zverev is the youngest semi-finalist at the ATP Finals since Juan Martin del Potro in 2009.
Novak Djokovic is chasing a sixth ATP Finals title and his first in the prestigious season-ending event at London's O2 Arena since 2015.
Roger Federer and Novak Djokovic, along with six fellow tennis stars travelled to Westminster by the London Underground.
Roger Federer has not been at his best all week, dropping sets in the two opening matches of his wobbly title defence.
Novak Djokovic is in sparkling form, winning Wimbledon, the Cincinnati Masters and US Open in recent months, after having elbow surgery in February.
Earlier this week, Fernando Verdasco had berated a ball boy at the Shenzhen Open for failing to bring his towel fast enough.
