Moscow Destroyed
Is Moscow was destroyed by an Atomic bomb in January 1945, then several things would happen immediately.
1. There would be extreme political confusion in the Soviet Union.
2. The Western Allies would have to stop an consider their options.
3. The Nazis would celebrate, but have to decide what to do next.
Moscow was the center of the Soviet Government. Assuming Stalin was in the city, the entire government would have been wiped out in one stroke. The military commanders led by Zhukov would have to take over as they would be the only ones with an organizational structure to do so. After seeing what the Nazis would do, they would launch an immediate full scale attack on German forces all along the lines. Red Armies would remain in close contact regardless of losses knowing that if the Nazis have another bomb they could have to use it on their own troops to kill Russians. The Russians know they have the numbers to come out on top if the Nazis can make further Atomic attacks.
The Western Allies would be torn. The British Government, except for Churchill, would seek a swift end to the war as England is extremely vulnerable to Atomic attacks. Churchill would want to continue the fight, knowing that any peace with the Nazis would be a victory for them as they would build up an Atomic arsenal and rain death on England sooner rather then later.
The United States would be Churchill's salvation. The Manhattan Project would be accelerated, and testing the first bomb would be done on Berlin. There would be no moral objection after Moscow, and the scientist time wasting habit of "admiring the problem" would be put aside because the stakes would be so much higher. A bomb could in theory be ready by March.
Hitler would be celebrating the destruction of Moscow, and would expect the West to sue for peace. If he doesn't have another bomb he would instead receive increased allied bombing of any target even remotely useful to his atomic program. Considerations in avoiding German civilian casualties would soon become a thing of the past as electrical plants, dams, factories, and anything remotely technological would be destroyed.
There would be no possibility of a cease fire. The Nazis have made it clear what their continued existence would mean for the rest of the world.
In order for the Nazis to have built a bomb at all other projects would have had to have been sacrificed. We can imagine that the Nazis don't have V-1 or V-2 rockets, jet fighters, or even Tiger tanks.