smile vs turn the corners of one's mouth down

smile

verb
  • To have (a smile) on one's face. 

  • To express by smiling. 

  • To express amusement, pleasure, or love and kindness. 

  • To be propitious or favourable; to countenance. 

  • To look cheerful and joyous; to have an appearance suited to excite joy. 

noun
  • Favour; propitious regard. 

  • A facial expression comprised by flexing the muscles of both ends of one's mouth, often showing the front teeth, without vocalisation, and in humans is a common involuntary or voluntary expression of happiness, pleasure, amusement, goodwill, or anxiety. 

turn the corners of one's mouth down

How often have the words smile and turn the corners of one's mouth down occurred in a corpus of books? (source: Google Ngram Viewer )