placidness       
noun [ U ] uk/ˈplæs.ɪd.nəs/ us/ˈplæs.ɪd.nəs/ (also placidity, /pləˈsɪd.ə.ti/ /pləˈsɪd.ə.t̬i/)
 宁静;平和
the quality of being calm
  the placidness of Monet's garden 莫奈的花园的宁静 
 See: placid
 - More examples
 - The aggressive near-brutality of the earlier concertos is tempered by a dreamlike placidity , with trilling birds acting as periodic wake-up calls.
 - The old woman, her eyes unblinking, regarded him coldly, with an eerie, almost supernatural placidity.