I hope you are all well.
He stopped to smoke.
Is to smoke a complement of stop or is it an infinitive-of-purpose adjunct?
It means that he wanted to smoke and he stopped for that purpose.If you use gerund in the sentence you mean that he gave up smoking. and you can take a close look at " https://dictionary.cambridge.org/tr/dilbilgisi/ingiliz-dilbilgisi/verb-patterns/stop-ing-form-or-to-infinitive "
i hope i could help.Have a good day.