i have created the custom module in which i want run cron Scheduled. please can any one help that is may code on submission:

public function submitForm(array &$  form, FormStateInterface $  form_state) {         $  to = 'a***@gmail.com';         $  params['subject'] = t('Drupal SMTP test e-mail');         $  params['body'] = array(t('If you receive this message it means your site is capable of using SMTP to send e-mail.'));         $  account = \Drupal::currentUser();         \Drupal::service('plugin.manager.mail')->mail('simple_mail', 'simple_mail', $  to, $  account->getPreferredLangcode(), $  params);         drupal_set_message(t('A test e-mail has been sent to @email via SMTP. You may want to check the log for any error messages.', ['@email' => $  to]));          return $  form; } 

i want add cron settings in it to schedule my mails.