Configurational thermostat

The effects of thermostats on the transport properties of simple fluids continue to be explored. In particular the configurational thermostat is studied in NEMD simulations to address a number of shortcomings of previous work that used profile biased kinetic thermostats. Delhommelle et al.242 perform... 

For the finite-temperature simulations, the temperature of the Si ions were controlled with a chain of five, linked Nose-Hoover thermostats." Because the electrons are always quenched back onto the Born-Oppenheimer surface after every timestep, no additional thermostat is needed for the electrons. Details of the configurations were similar to those with the CP scheme, except that the in-plane cells consisted of 16 atoms per layer and the basic timestep of the simulation was 100 a.u. 

The simple control scheme in Figure 2.103 measures the temperature difference (ATC-1) between the solar collector temperature and the solar water tank temperature, starts the water pump when AT > 20°C, and stops it when this temperature difference drops to 10°C. The variable-speed refrigerant pump circulation is similarly controlled. Because the condenser (lake, well, or swamp) temperature is more or less constant, AT control might not be essential and measuring only the evaporator (solar water tank temperature) by a standard thermostat (TC-2) can be sufficient. In this configuration, the refrigerant pump is started whenever the solar tank temperature is above 60°C (140°F), and the pump speed is increased to its maximum, as the temperature in the solar hot water tank reaches, say, 70°C (160°F). 

To study the dependence of the reaction rates on the constitution and configuration of the ozonides, an automatic method was worked out. Ozonides, dissolved in absolute methanol which was saturated with the barium salt of the acid produced in the reaction (mainly barium acetate or barium benzoate), were heated in a thermostat to 50°C. In a Combi-titrator (Methrom Co.) a methanol solution of barium methylate (0.1 N) was added automatically at such speed that the pH of the solution remained unchanged. The variation in the volume of added methylate solution with reaction time was registered on chart paper. The reactions were carried out under pure nitrogen, and the curves always showed first-order kinetics. 

Constant temperatnre is maintained by Nose-Hoover thermostat and the equations of motion were integrated using the two time scale r-RESPA with a large time step of 2 fs and a small time step of 0.2 fs. Equilibration using these initial configurations was then carried out for at least 2 ns before beginning any produc-... 

Tensile tests at low to intermediate displacement rates (i.e. 1, 10, 100 and 500 mm/min) were performed by an Instron tensile tester model 4502 equipped with a 1 kN load cell. Temperature in the range from 0°C to 70°C was controlled by an Instron thermostatic chamber model 3119. Tests at the moderately high displacement rate of 60000 mm/min (1 m/s) were carried out at room temperature by an instrumented CEAST impact pendulum in the tensile configuration. Load data were collected at a sampling time of 30 p.s and load vs displacement curves were provided directly by the CEAST software (DAS 4000 Extended Win Acquisition System Ver. 3.30). 

Simulation baths of = 108 Lennard-Jones (LJ) particles with e/ks = 90K, a = 3.405A and mass m = 39.94 amu were used. The density of the systems was pa = 0.844 and the temperature of the systems was set to kT = 300 K by coupling each degree of freedom to a GGMT thermostat. Production runs of 200 ps were performed before and after the addition of the N + V particle and this configuration was used as the initial configuration for both A-AFED simulations and thermodynamic integration [55,56]. 

Schematic of a three-way liquid phase reactor setup. The setup can be operated as a TS-PFR in the configuration shown or converted to a TS-CSTR or a TS-BR by replacing the reactor coil in the thermostat with a stirred vessel.

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