An MD11 Captain reported that after landing the forward cabin and cockpit filled with smoke. The aircraft was evacuated.

Narrative

After a uneventful landing the cockpit crew smelled a strong odor of ammonia. As I slowed to taxi speed and began to turn off runway one of the jumpseaters came up to report that there was smoke in the jumpseat area. I told my IRO to go back and investigate. I took control of radios and told Tower we have smoke in aircraft. He said he was rolling the trucks. As I taxied the smoke became much thicker and started to overtake the cockpit. I stopped straight ahead and ordered an evacuation of the aircraft out the left side and to meet at the nose of the aircraft. My IRO blew the slide. My First Officer started to look for the evacuation checklist but I instructed him to leave the aircraft and I ran some of the checklist from memory. I set parking brake; shut down all three engines and blew the bottles to the engines. We all evacuated the aircraft and when we met at the nose of the aircraft Airport Rescue and Fire Fighting was just arriving. We had no known hazmat on aircraft. I asked everyone if they were OK from the evacuation or the fumes. Everyone said they were and we all declined medical assistance. We waited for Airport Rescue and Fire Fighting to clear the aircraft so we could then clear customs.