The dimer method of Henkelman and Jónsson with improvements by Heyden et al and Kästner and Sherwood for estimating the lowest eigenmode using only first derivatives. [1] [2] [3]
The solid state dimer module extends this method to solid state phase transitions. [4]
The SSDimer_atoms is an atomslike class, which defines suitable set_positions(), get_positions(), get_forces() for the solidstate dimer (SSDimer) method to include cell degrees of freedom in saddle search. It becomes the regular dimer by setting “ss=False”. External stress tensor can be applied by setting “express” to find saddles on enthalpy surfaces.
phi_tol = 5, rotationMax = 4, ss = False, express=np.zeros((3,3)), rotationOpt = ‘cg’, weight = 1):
Example:
from tsase.dimer import ssdimer d = ssdimer.SSDimer_atoms(R0 = p, rotationMax = 10, phi_tol=3, ss = True) ### Use quickmin optimizer in ssdimer d.search(minForce = 0.0001, movie = "dimer2.movie", interval = 20 ) ### Or use other first order optimizer in ase. ### Second order optimizers cannot be used when "ss = True". #dyn = MDMin(d) #dyn.run(fmax=0.0001)
References
[1] 

[2] 

[3] 

[4] 
