Understanding the microscopic mechanisms of new particle formation under acid-rich conditions is significance in atmospheric science. Using quantum chemistry calculations, we investigated mechanism methanesulfonic acid (MSA)–methylamine (MA)–ammonia (NH 3 ) clusters. We focused on binary (MSA) 2n -(MA) n and ternary 3n -(NH , ( = 1–4) systems which contain more than base molecules. found that l...