# min_style cg command # min_style hftn command # min_style sd command # min_style quickmin command # min_style fire command # [min_style spin](min_spin) command # [min_style spin/cg](min_spin) command # [min_style spin/lbfgs](min_spin) command ## Syntax min_style style - style = *cg* or *hftn* or *sd* or *quickmin* or *fire* or *spin* or *spin/cg* or *spin/lbfgs* *spin* is discussed briefly here and fully on `min_style spin `__ doc page *spin/cg* is discussed briefly here and fully on `min_style spin `__ doc page *spin/lbfgs* is discussed briefly here and fully on `min_style spin `__ doc page ## Examples ``` LAMMPS min_style cg min_style fire min_style spin ``` ## Description Choose a minimization algorithm to use when a [minimize](minimize) command is performed. Style *cg* is the Polak-Ribiere version of the conjugate gradient (CG) algorithm. At each iteration the force gradient is combined with the previous iteration information to compute a new search direction perpendicular (conjugate) to the previous search direction. The PR variant affects how the direction is chosen and how the CG method is restarted when it ceases to make progress. The PR variant is thought to be the most effective CG choice for most problems. Style *hftn* is a Hessian-free truncated Newton algorithm. At each iteration a quadratic model of the energy potential is solved by a conjugate gradient inner iteration. The Hessian (second derivatives) of the energy is not formed directly, but approximated in each conjugate search direction by a finite difference directional derivative. When close to an energy minimum, the algorithm behaves like a Newton method and exhibits a quadratic convergence rate to high accuracy. In most cases the behavior of *hftn* is similar to *cg*, but it offers an alternative if *cg* seems to perform poorly. This style is not affected by the [min_modify](min_modify) command. Style *sd* is a steepest descent algorithm. At each iteration, the search direction is set to the downhill direction corresponding to the force vector (negative gradient of energy). Typically, steepest descent will not converge as quickly as CG, but may be more robust in some situations. Style *quickmin* is a damped dynamics method described in [(Sheppard)](Sheppard), where the damping parameter is related to the projection of the velocity vector along the current force vector for each atom. The velocity of each atom is initialized to 0.0 by this style, at the beginning of a minimization. Style *fire* is a damped dynamics method described in [(Bitzek)](Bitzek), which is similar to *quickmin* but adds a variable timestep and alters the projection operation to maintain components of the velocity non-parallel to the current force vector. The velocity of each atom is initialized to 0.0 by this style, at the beginning of a minimization. This style correspond to an optimized version described in [(Guenole)](Guenole) that include different time integration schemes and default parameters. The default parameters can be modified with the command [min_modify](min_modify). Style *spin* is a damped spin dynamics with an adaptive timestep. Style *spin/cg* uses an orthogonal spin optimization (OSO) combined to a conjugate gradient (CG) approach to minimize spin configurations. Style *spin/lbfgs* uses an orthogonal spin optimization (OSO) combined to a limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) approach to minimize spin configurations. See the [min/spin](min_spin) page for more information about the *spin*, *spin/cg* and *spin/lbfgs* styles. Either the *quickmin* or the *fire* styles are useful in the context of nudged elastic band (NEB) calculations via the [neb](neb) command. Either the *spin*, *spin/cg*, or *spin/lbfgs* styles are useful in the context of magnetic geodesic nudged elastic band (GNEB) calculations via the [neb/spin](neb_spin) command. :::: note ::: title Note ::: The damped dynamic minimizers use whatever timestep you have defined via the [timestep](timestep) command. Often they will converge more quickly if you use a timestep about 10x larger than you would normally use for dynamics simulations. For *fire*, the default timestep is recommended to be equal to the one you would normally use for dynamics simulations. :::: :::: note ::: title Note ::: The *quickmin*, *fire*, *hftn*, and *cg/kk* styles do not yet support the use of the [fix box/relax](fix_box_relax) command or minimizations involving the electron radius in [eFF](pair_eff) models. :::: ------------------------------------------------------------------------ Styles with a *gpu*, *intel*, *kk*, *omp*, or *opt* suffix are functionally the same as the corresponding style without the suffix. They have been optimized to run faster, depending on your available hardware, as discussed on the [Accelerator packages](Speed_packages) page. The accelerated styles take the same arguments and should produce the same results, except for round-off and precision issues. These accelerated styles are part of the GPU, INTEL, KOKKOS, OPENMP, and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the [Build package](Build_package) page for more info. You can specify the accelerated styles explicitly in your input script by including their suffix, or you can use the [-suffix command-line switch](Run_options) when you invoke LAMMPS, or you can use the [suffix](suffix) command in your input script. See the [Accelerator packages](Speed_packages) page for more instructions on how to use the accelerated styles effectively. ------------------------------------------------------------------------ ## Restrictions The *spin*, *spin/cg*, and *spin/lbfgps* styles are part of the SPIN package. They are only enabled if LAMMPS was built with that package. See the [Build package](Build_package) page for more info. ## Related commands [min_modify](min_modify), [minimize](minimize), [neb](neb) ## Default ``` LAMMPS min_style cg ``` ------------------------------------------------------------------------ ::: {#Sheppard} **(Sheppard)** Sheppard, Terrell, Henkelman, J Chem Phys, 128, 134106 (2008). See ref 1 in this paper for original reference to Qmin in Jonsson, Mills, Jacobsen. ::: ::: {#Bitzek} **(Bitzek)** Bitzek, Koskinen, Gahler, Moseler, Gumbsch, Phys Rev Lett, 97, 170201 (2006). ::: ::: {#Guenole} **(Guenole)** Guenole, Noehring, Vaid, Houlle, Xie, Prakash, Bitzek, Comput Mater Sci, 175, 109584 (2020). :::