Loading doc/src/compute_hma.txt +21 −3 Original line number Diff line number Diff line Loading @@ -37,8 +37,24 @@ energy, pressure or heat capacity), using the harmonically-mapped averaging (HMA) method. This command yields much higher precision than the equivalent compute commands ("compute pe"_compute_pe.html, "compute pressure"_compute_pressure.html, etc.) commands during a canonical simulation of an atomic crystal. commands during a canonical simulation of an atomic crystal. Specifically, near melting HMA can yield averages of a given precision an order of magnitude faster than conventional methods, and this only improves as the temperatures is lowered. This is particularly important for evaluating the free energy by thermodynamic integration, where the low-temperature contributions are the greatest source of statistical uncertainty. Moreover, HMA has other advantages, including smaller potential-truncation effects, finite-size effects, smaller timestep inaccuracy, faster equilibration and shorter decorrelation time. HMA should not be used if atoms are expected to diffuse. It is also restricted to simulations in the NVT ensemble. Computation of the heat capacity with this compute is presently restricted to the "lj_smooth_linear"_lj_smooth_linear.html pair style. Use with other pair styles requires an additional method (single2nd) to be implemented in the corresponding Pair class. Computation of the energy and pressure does not have this restriction. In this method, the analytically known harmonic behavior of a crystal is removed from the traditional ensemble averages, which leads to an accurate and precise measurement of the anharmonic contributions without contamination Loading Loading @@ -119,7 +135,9 @@ NOTE: Compute hma should be used when the atoms of the solid do not diffuse. Dif NOTE: The "fix_modify energy yes"_fix_modify.html command must also be specified if a fix is to contribute potential energy to this command. :line An example input script that uses this compute is included in examples/USER/hma/ along with corresponding LAMMPS output showing that the HMA properties fluctuate less than the corresponding conventional properties. [Output info:] Loading Loading
doc/src/compute_hma.txt +21 −3 Original line number Diff line number Diff line Loading @@ -37,8 +37,24 @@ energy, pressure or heat capacity), using the harmonically-mapped averaging (HMA) method. This command yields much higher precision than the equivalent compute commands ("compute pe"_compute_pe.html, "compute pressure"_compute_pressure.html, etc.) commands during a canonical simulation of an atomic crystal. commands during a canonical simulation of an atomic crystal. Specifically, near melting HMA can yield averages of a given precision an order of magnitude faster than conventional methods, and this only improves as the temperatures is lowered. This is particularly important for evaluating the free energy by thermodynamic integration, where the low-temperature contributions are the greatest source of statistical uncertainty. Moreover, HMA has other advantages, including smaller potential-truncation effects, finite-size effects, smaller timestep inaccuracy, faster equilibration and shorter decorrelation time. HMA should not be used if atoms are expected to diffuse. It is also restricted to simulations in the NVT ensemble. Computation of the heat capacity with this compute is presently restricted to the "lj_smooth_linear"_lj_smooth_linear.html pair style. Use with other pair styles requires an additional method (single2nd) to be implemented in the corresponding Pair class. Computation of the energy and pressure does not have this restriction. In this method, the analytically known harmonic behavior of a crystal is removed from the traditional ensemble averages, which leads to an accurate and precise measurement of the anharmonic contributions without contamination Loading Loading @@ -119,7 +135,9 @@ NOTE: Compute hma should be used when the atoms of the solid do not diffuse. Dif NOTE: The "fix_modify energy yes"_fix_modify.html command must also be specified if a fix is to contribute potential energy to this command. :line An example input script that uses this compute is included in examples/USER/hma/ along with corresponding LAMMPS output showing that the HMA properties fluctuate less than the corresponding conventional properties. [Output info:] Loading
