There is an argument to MIRT called CONTROL:
mirt(data, model, itemtype = NULL, guess = 0, upper = 1,
SE = FALSE, covdata = NULL, formula = NULL, SE.type = "Oakes",
method = "EM", optimizer = NULL, dentype = "Gaussian",
pars = NULL, constrain = NULL, parprior = NULL, calcNull = FALSE,
draws = 5000, control = list()
CONTROL: a list passed to the respective optimizers (i.e., optim(), nlminb(), etc). Additional arguments have been included for the 'NR' optimizer: 'tol' for the
convergence tolerance in the M-step (default is TOL/1000), while the default
number of iterations for t