If you are an atheist, when you die, what would make you think that you would end up in heaven? That is ludicrous. Would you want to suddenly spend years with someone whom for most of your life you have never talked to, ignored, and even denied their existence? Well, as an atheist, that is how you have been acting towards God, so when you die, you will realize how dreadful that you have acted towards the all loving and caring God.
At the time of death you will of course believe in God, and at the same time feel such a dreadful shame that you will not want to face Him. It is you who will actually banish yourself from His presence. Since God dwells in Heaven, you will choose the opposing dwelling place, which is Hell. Of course God will sentence you to that place, but it will be what you have sought all your life, to be out of Gods presence, so it will be only natural for you to want to continue in that manner despite the dire circumstances.
Of course most atheists, though they want to pretend that they are just as moral and upstanding as any Christian, in most instances have some underlying depravity that does not jive with recognizing that there is a Supreme Being that has set in place certain laws which all men are bound to follow, so there will of course be the other physical punishments that will be part of the Hell that you as an atheist will have chosen.
Of course God gave you a free will, and also an inherent ability to know that there must be a God from the beauty and order observed in nature and the universe. Using Evolution as a crux for trying to deny a Creator is not ever able to be totally convincing for anyone. But as long as you still have life, you are free to use that free will to change the road that you are following on your way to Hell. Hopefully you will at some point make that necessary change before it is over. The choice though is entirely yours.