Hello lammps developers,

I have a question about the integrate equations for npt ensemble, for the

fix npt is use the Trotter factorization of the Liouville operator. If I

understand the scheme of integration can summarized as following:

nhc_press_integrate(); (thermostat and propagated the barostat velocities)

nhc_temp_integrate(); (thermostat and propagated the particles velocities)

nh_omega_dot(); (barostat propagation the barostat velocities)

nh_v_press(); (barostat scaled and propagation the the particles velocities)

nve_v(); (verlet propagation of particles velocities)

remap(); (barostat propagation of box)

nve_x(); (verlet propagation the particles positions)

remap(); (barostat propagation of box)

nve_v(); (verlet propagation of particles velocities)

nh_v_press(); (barostat propagation the the particles velocities)

nh_omega_dot(); (barostat propagation the barostat velocities)

nhc_temp_integrate(); (thermostat and propagated the particles velocities)

nhc_press_integrate(); (thermostat and propagated the barostat velocities)

I read the another list archives related to this issue, you mention the

Tuckerman paper (Tuckerman, Alejandre, Lopez-Rendon, Jochim, and Martyna,

J Phys A: Math Gen, 39, 5629 (2006)) the factorization is similar to, but

not identical to, the factorization described by Tuckerman et al., in the

motions equations to sampling the npt ensemble the barostat scaled the

particles positions similar to the particles velocities, in which part of

code take account this. I have another doubt the lammps use upper

triangular matrix to describe the box and symmetric virial stress tensor,

is possible use both together?, because with only one of those

constriction the cell rotation is eliminated.

Thanks

Samuel