csmath: Solid and passive Semi-Slav line with white having clear intention to grab as much space as he can - usual play in Slav/Semi-Slav anyway. He will give away a-file in this variation.
[new move? but white will close the position so this will not be useful.]
[Svidler switches gears underlining his space advantage and showing black that he could attack black king as well. This now becomes difficult for black to ignore while crammed up on the queenside. Strange enough the weakening of black castling is going to play very important role in choice of 39th move of black.]
[Motylev played model defence and it looks like he has countergame. However his pawn weaknesses are there to stay so my personal feeling is that white has serious practical advantage. I have to say I do not like to play Slav as black.]
[I have to say I have no idea what Motylev intends as he already controls a-file and cannot really play Ra1 under any circumstances.]
[Yet another strange move without any particular reason. As Kasparov would say "27. ...b5 suggests itself."
In either case both players keep on manouvreing without making any particular plan while doing that. Obviously white has more space to really improve position of his pieces.]
[horrible positional move, clearly an error in my view since now the eventual ending will surely be in white favor.]
39. Qd3! Qxd3
[Motylev goes into ending that is clearly going to be worse for black.
39. ...Qa8 is not possible because of
40. Nxe6! fxe6?
41. Qg6 with surprising but decisive attack.]
[Motylev does not want to wait with 42. ...Rc7 but this is not helping in any way.]
[black is already lost and this is only making that loss faster. 50. ...Rb3, 51. Ne2 Kf7, 52. Rc7 looks hopeless as well.]
If you play Slav/Semi-Slav you gotta be patient and prepared on long grueling defence. Looks like Motylev was just not in that mode here.