Many harmonon soft modes are found and they can be used to explain why that barium titanate crystal has a and c domain structures in ferroelectric phase transition while temperature rde-duces.

• 用复合空间型方法,在自由边界条件下解出了钛酸钡有限尺寸晶体的简谐振动方程,发现许多简谐子软模。