With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Steven Tyler has never had a drug addiction problem.
text_B: Quantum chemistry composite methods -LRB- also referred to as thermochemical recipes -RRB- are computational chemistry methods that aim for high accuracy by combining the results of several calculations .. computational chemistry. computational chemistry. They combine methods with a high level of theory and a small basis set with methods that employ lower levels of theory with larger basis sets .. basis set. basis set ( chemistry ). They are commonly used to calculate thermodynamic quantities such as enthalpies of formation , atomization energies , ionization energies and electron affinities .. They aim for chemical accuracy which is usually defined as within 1 kcal / mol of the experimental value .. The first systematic model chemistry of this type with broad applicability was called Gaussian-1 -LRB- G1 -RRB- introduced by John Pople .. John Pople. John Pople. This was quickly replaced by the Gaussian-2 -LRB- G2 -RRB- which has been used extensively .. The Gaussian-3 -LRB- G3 -RRB- was introduced later .
not_related.