text: Using three pi-conjugated molecules, yo
  (1,3,5-hexatriene, 1-formyl-6-hydroxyhexa-1,3,5-triene, and 1,1-diamino-6,6-dinitrohexa-1,3,5-triene),
  We be delvin' into ab initio theory, no lie
  To get them reliable values, oh my
  
  Linear and nonlinear optical properties, we seek
  With a focus on them vibrational contributions, unique
  Known to be important or got potential, you know
  We make these calculations feasible, let's go
  
  Field-induced coordinates, we got the technique
  Combined with a finite field procedure, it's sleek
  For most purposes, MP2/6-31+G(d) level be fine
  But let me tell ya 'bout our results, it's prime
  
  We checked the convergence, that perturbation treatment
  For vibrational anharmonicity, we went deep in it
  In most cases, it starts to converge, no doubt
  But hold up, we found a problematic situation, shout it out!