Ding Liren and Shakhriyar Mamedyarov still lead, but there are now six players who are half a point back.

Shakhriyar Mamedyarov of Azerbaijan and Ding Liren of China continue to lead the Moscow Grand Prix after both drew in Round 6 on Thursday, but there are now six players within a half point of the leaders.

Ding drew a hard-fought, roller-coaster game with Maxime Vachier-Lagrave of France, while Mamedyarov agreed to an early peace with Teimour Radjabov, a compatriot. Ding and Mamedyarov now have 4 points apiece.

There were three decisive games in Round 6: Boris Gelfand of Israel beat Pentala Harikrishna of India, Hikaru Nakamura of the United State defeated Ian Nepomniachtchi of Russia, and Michael Adams of England beat Ernesto Inarkiev of Russia.

The victories by Gelfand and Nakamura moved them into the group of players who trail the leaders by half a point. The group also includes Radjabov, Vachier-Lagrave, and Peter Svidler and Alexander Grischuk, who are both from Russia.

The Moscow Grand Prix is the second in a series of four tournaments. The top two finishers will qualify for the Candidates tournament next year to select a challenger for the World Championship.

Twenty-four of the top players in the world are competing in the Grand Prix, with 18 playing in each tournament. (Each player competes in three of the four competitions.)

Ding nearly grabbed the sole lead, but he was unable to put Vachier-Lagrave away after playing brilliantly early in the game.

Ding Liren vs. Maxime Vachier-Lagrave
FIDE Grand Prix Moscow | Moscow RUS | Round 6.1 | 18 May 2017 | ECO: A20 | 1/2-1/2
1. c4 e5 2. g3 Nf6 3. Bg2 d5 4. cxd5 Nxd5 5. Nf3 Nc6 6. O-O Nb6 7. Nc3 Be7 8. a3 O-O 9. b4 Re8 10. e3 a6 11. Qc2 Bg4 12. Ne4 f5 13. Nc5 e4 14. Ne1 Be2 15. d3 Bxf1 16. Kxf1 Bxc5 17. bxc5 Nd7 18. dxe4 fxe4 19. Bxe4 Qe7 20. Bxh7+ Kh8 21. Bg6 Rf8 22. Rb1 Nxc5 23. Ng2 Rad8 24. Nf4 Ne6 25. Rxb7 Ne5 Ding's ingenious exchange sacrifice has paid dividends and he has a clear edge. But, precise play is needed to win.
26. Bb2?!
26. Be4! Nc5 27. Bb2! White has a huge advantage.
27... Nxb7 28. Bxe5 The threat of Ng6 compels Black to play:
28... Rxf4 29. exf4 Black's king will soon be mated.  )
26... Nf3?!
26... Nxf4! 27. gxf4 Nxg6 28. Qxg6 Rb8! Would allow Black to survive.  )
27. Bh5 Nxf4 28. gxf4 Rd2 29. Qc3
29. Qg6! This move would have been decisive.  )
29... Nxh2+ 30. Kg1? White needed to make one more precise move to convert his edge to a decisive advantage.
30. Ke1 White should win.  )
30... Rxf4! Excellent defense and very resourceful. Every Black piece is attacked but none can be taken!
31. Qxg7+
31. Qxd2? Qg5+ 32. Kh1 Qxh5  )
31. Kxh2 Qh4+  )
31. exf4 Qe1+ 32. Kxh2 Rxf2+ 33. Kh3 Qh1+ 34. Kg4 Rg2+ 35. Kf5 Qxh5+  )
31... Qxg7+ 32. Bxg7+ Kxg7 33. exf4 Kh6 34. Kxh2 Kxh5 35. Rxc7 Kg4 Black is able to defend the rook ending.
36. Kg2 Rd3 37. f3+ Kh5 38. a4 Rd4 39. Rc5+ Kh4 40. Kf2 Rxa4 41. Ke3 a5 42. Rg5 Ra3+ 43. Ke4 Ra4+ 44. Ke5 Rb4 45. Rg4+ Kh5 46. f5 Rb5+ 47. Ke6 Rb6+ 48. Ke7 Rb7+ 49. Ke6 Rb6+ 50. Kf7 Rb7+ 51. Kg8 Rb8+ 52. Kg7 Rb7+

Nakamura and Gelfand both played very well in their wins:

Boris Gelfand vs. Pentala Harikrishna
FIDE Grand Prix Moscow | Moscow RUS | Round 6.6 | 18 May 2017 | ECO: E06 | 1-0
1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. g3 Be7 5. Bg2 O-O 6. O-O dxc4 7. Qc2 a6 8. a4 Bd7 9. Bg5 Bc6 10. Rd1 Nbd7 11. Nbd2 h6 12. Bxf6 Nxf6 13. Nxc4 Be4 14. Qc1 a5 15. Nfe5 Bxg2 16. Kxg2 c6 17. Qc2 Qc7 18. Rac1 Rfd8 19. Qb3 Bf8 20. Qf3 Rac8 21. e4 b5 22. Ne3 Qb7 23. b3 c5? Harikrishna must have overlooked something or miscalculated. Black was not ready to make this push.
23... Bb4 White's position is a little more pleasant but Black would still be very solid.  )
24. d5! Thematic and strong.
24... exd5 25. Nxd5! Rd6
25... Nxd5 26. exd5 And the White knight will eventually land on c6.  )
26. axb5! Qxb5 Black's position is suspect on strategic grounds because he has an inferior pawn structure and a bad bishop, but Gelfand attacks an even more serious weakness.
27. Nxf7! Kxf7 28. e5 Re6 29. exf6 White is up a pawn, has a safer king, a better minor piece, and a dominant position. His advantage is overwhelming.
29... g6
29... gxf6 30. Qh5+ Kg8 31. Qg4+ Kf7 32. Nf4  )
30. Re1 Qc6 31. Rxe6 Qxe6 32. Ra1 Qf5 33. Rxa5 Qxf3+ 34. Kxf3 Rb8 35. Ke4 Rxb3 36. Ra7+ Ke6 37. Nf4+ This move was a little imprecise.
37. f4 Would have been more effective.
37... c4 38. g4  )
37... Kxf6 38. Ra6+ Kf7 39. Ra7+ Kf6 40. Ra6+ Kf7 41. Nxg6 Bg7 42. f4 Rb2 43. h4 Rg2?
43... h5! This move would have allowed Black to fight on as he can try to target g3 as a weakness and White would not be able to play g4. I doubt that Black could avoid losing, but it was worth a try.  )
44. Kf3 Rg1 45. h5 The rest was not difficult for Gelfand.
45... c4 46. Ra7+ Kg8 47. Ne7+ Kf8 48. Ng6+ Kg8 49. Rc7 Rc1 50. Ne7+ Kf8 51. Nf5 Bb2 52. Rc8+
Hikaru Nakamura vs. Ian Nepomniachtchi
FIDE Grand Prix Moscow | Moscow RUS | Round 6.4 | 18 May 2017 | ECO: B97 | 1-0
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bg5 e6 7. f4 Qb6 8. a3 Nc6 9. Nb3 Be7 10. Qd2 O-O 11. O-O-O Rd8 12. Bd3 h6 13. h4 Bd7 Black has a pretty good position arising the Rauzer Variation, but I've never trusted these positions. Nakamura begins to play very energetically and Black is soon in difficulty.
14. Qe2! Preparing e5, which is not easy to prevent.
14... Kf8 A typical idea. Black wants to play hxg5 now that he has cleared the g8 square. But it is still very risky.
14... Qc7 15. g4! And Black is in trouble. For example:
15... b5 16. Bxf6 Bxf6 17. e5 dxe5 18. g5 And Black cannot survive.  )
15. e5! An energetic and strong move.
15... dxe5 16. fxe5 hxg5 The best practical move.
16... Nd5 17. Nxd5 exd5 18. Bxe7+ Would be a very depressing position for Black.  )
17. exf6 Bxf6 18. hxg5 Bxg5+ 19. Kb1 Strategically, White is dead lost: Black has an extra pawn, a perfect pawn structure, a bishop pair, and active pieces. But none of that matters if the Black king is mated!
19... Qe3 20. Qh5! Bh6 21. Rhf1! White organizes his attack.
21... Be8 22. Rde1 Qg5 23. Qh3! White threatens to play Ne4 and Nbc5. Black has no good way to relieve the pressure on his position.
23... Ne5 24. Nc5! Kg8
24... Ke7 25. Bf5 Would be terrible for Black.  )
25. Nxe6! Well calculated.
25... fxe6 26. Qxe6+ Nf7
26... Bf7 This was a better try, but after:
27. Qxe5 Qxe5 28. Rxe5 White retains excellent winning chances because of his extra pawn.  )
27. Bg6! Black must lose the knight on f7.
27... Kh8
27... Rd7 28. Qxe8+! A nice resource  )
28. Bxf7 Bxf7 29. Qxf7 Qxg2 30. Rg1 Qd2 31. Rd1 Qf4 32. Qxb7 White is up a pawn and Black's king is not safe. It was not difficult for Nakamura to convert his edge to a win.
32... Rdb8 33. Qe4 Qf8 34. Rg6 Ra7 35. Qd4

It’s the sign of a true champion when a player who is not playing his best can recover from disappointments and still fight. Adams was coming off three consecutive losses and in last place. But he pulled himself together and won a fine game against Inarkiev:

Michael Adams vs. Ernesto Inarkiev
FIDE Grand Prix Moscow | Moscow RUS | Round 6.9 | 18 May 2017 | ECO: C84 | 1-0
1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. d3 b5 7. Bb3 d6 8. a3 O-O 9. Nc3 Nb8 10. a4 b4 11. Nd5 Nxd5 12. Bxd5 c6 13. Bb3 Nd7 14. Be3 Bb7 15. a5 d5 16. d4 dxe4 17. Nxe5 Nf6 18. Qe2 Qc7 19. Bf4 Bd6 20. Bg3 c5 21. c3 Rac8 22. Rfd1 g6 23. Qe3 White's knight on e5 and active pieces give him a slight edge, but it's not a huge deal. But Inarkiev needed to play precisely to avoid trouble.
23... cxd4?
23... bxc3! This move was best as it would have opened more lines on the queenside for Black. After:
24. bxc3 cxd4 25. cxd4 Bd5! White's advantage is kept to a minimum.  )
24. cxd4 Black lacks counterplay.
24... Nd5
24... Bd5 The analogous move to the previous variation now fails because after:
25. Bxd5 Nxd5 26. Qxe4 Black cannot play Nc3  )
25. Qh6! The invasion begins!
25... Qe7
25... f6 26. Nxg6 Bxg3 27. Nxf8 And White has a decisive edge.  )
26. Re1! f5 27. f3! White blasts the position wide open.
27... Bxe5 A sad move for Black to have to make, but what else could he have done? The threat was fxe4.
27... f4 28. Bh4 Qg7 29. Qxg7+ Kxg7 30. fxe4 Black has no hope of surviving.  )
27... exf3 28. Nxg6!  )
28. Bxe5 exf3 29. gxf3 The dust has settled and one look at the bishop on e5 is enough to know what the outcome should be.
29... Rfe8 30. Rac1 Qf8 31. Qg5 Qf7 32. Kf2 h5 33. Bd6 Rxe1 34. Rxe1 Re8 35. Rc1 Re6 36. Bxd5! Not the only move for White to convert his advantage, but I like it for its simplicity. White creates a position with opposite-colored bishops and Black is unable to protect the dark squares, allowing White to infiltrate.
36... Bxd5 37. Rc8+!
37. Rc7 Rxd6 This also would have given White a decisive edge, but it was less clear cut.  )
37... Re8
37... Kh7 38. Rc7  )
38. Rc7 Qe6 39. Be5 Rc8 40. Rg7+ Kf8 41. Qh6 And that will be that
41... Rc2+ 42. Kg1

With eight players within a half point of each other for the lead and three rounds still to go, the tournament is still wide open. 

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Samuel Shankland is a United States grandmaster ranked No. 4 in the country. He is a professional player and recipient of the Samford Fellowship in 2013, the most prestigious award in the United States for young chess players. He was also a member of the team that won the gold medal at the 2016 Chess Olympiad. He is at @GMShanky on Twitter, has his own site, and is also on Facebook.