At 1345 central time, a Cessna 172M nosed over in a field during a precautionary landing near Vici. The pilot was not injured. The pilot reported that, while flying from Liberal, Kan., to Oklahoma City, he encountered ice throughout the airframe. He made an unscheduled landing at Woodward, Okla. After removing some of the ice, the pilot departed Woodward and again headed for Oklahoma City. He was cruising at 115 mph when he encountered freezing rain. Over the next 20 miles, the pilot observed the indicated airspeed decay progressively to 80 mph. He then initiated a descent to maintain 80 mph and diverted to Vici Municipal Airport. When he could no longer maintain 80 mph, he elected to land in an open field, during which time the landing gear collapsed and the airplane flipped inverted.