Azerbaijan's Naiditsch overcame GM Ziaur Rehman, while Karthikeyan, a two-time former National champion, defeated Vietnamese GM Tran Tuan Minh, rated 2547, to share the lead at 6.5 points after the seventh round.
Rehman had the white pieces in an original Reti-kind of an opening where the queens were traded off early in the middlegame to reach a rook vs. two minor pieces endgame.
Naiditsch was obviously pressing but it was more or less equal. Suddenly, for no clear reason, Rehman gave up his e- pawn after which it was the end for the Bangladeshi GM.
Double National Champion Karthikeyan also had an equal position with the black pieces out of a Kings Indian Defence opening against Vietnamese GM Tran Tuan Minh, rated 2547.
Karthikeyan, too, ended up with rook vs two minor pieces, being Tran with his double knights and Karthikeyan with a knight and bishop. The other big difference was that White had 4 pawns on the kingside against Karthikeyan's three, while, Karthikeyan had two pawns on the queenside against Tran's one.
This classic 'queenside pawn majority' was exploited well by the Indian who pushed them forward while the Vietnamese wasted his time with king moves giving Karthikeyan a winning advantage. The Indian grandmaster won without much ado.
In the sixth round, Naiditsch, rated 2701, notched up a fine win over GM Vaibhav Suri, while Karthikeyan, rated 2580, beat IM Himal Gusain and GM Ziaur Rehman settled for a quick draw with GM Deep Sengupta, rated 2586.
The C-category with a massive 1257 players got underway today. The players fight for a total prize money of Rs. 25 lakhs.
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