compute_translational_thermo Subroutine

public pure subroutine compute_translational_thermo(total_mass, temperature, pressure, E, S, Cv)

Compute translational contributions to thermodynamic properties.

Uses ideal gas partition function (Sackur-Tetrode equation for entropy). E_trans = 3/2 * R * T S_trans = R * [5/2 + ln((2pimkT/h^2)^(3/2) * k*T/P)] Cv_trans = 3/2 * R

Arguments

Type IntentOptional Attributes Name
real(kind=dp), intent(in) :: total_mass

Total mass in amu
real(kind=dp), intent(in) :: temperature

Temperature in K
real(kind=dp), intent(in) :: pressure

Pressure in atm
real(kind=dp), intent(out) :: E

Thermal energy in Hartree
real(kind=dp), intent(out) :: S

Entropy in cal/(mol*K)
real(kind=dp), intent(out) :: Cv

Heat capacity in cal/(mol*K)

Called by

proc~~compute_translational_thermo~~CalledByGraph proc~compute_translational_thermo compute_translational_thermo proc~compute_thermochemistry compute_thermochemistry proc~compute_thermochemistry->proc~compute_translational_thermo proc~compute_mbe compute_mbe proc~compute_mbe->proc~compute_thermochemistry proc~print_vibrational_analysis print_vibrational_analysis proc~compute_mbe->proc~print_vibrational_analysis proc~gmbe_pie_coordinator gmbe_pie_coordinator proc~gmbe_pie_coordinator->proc~compute_thermochemistry proc~gmbe_pie_coordinator->proc~print_vibrational_analysis proc~hessian_coordinator hessian_coordinator proc~hessian_coordinator->proc~compute_thermochemistry proc~hessian_coordinator->proc~print_vibrational_analysis proc~print_vibrational_analysis->proc~compute_thermochemistry proc~serial_gmbe_pie_processor serial_gmbe_pie_processor proc~serial_gmbe_pie_processor->proc~compute_thermochemistry proc~serial_gmbe_pie_processor->proc~print_vibrational_analysis proc~unfragmented_calculation unfragmented_calculation proc~unfragmented_calculation->proc~compute_thermochemistry proc~unfragmented_calculation->proc~print_vibrational_analysis interface~hessian_coordinator hessian_coordinator interface~hessian_coordinator->proc~hessian_coordinator interface~unfragmented_calculation unfragmented_calculation interface~unfragmented_calculation->proc~unfragmented_calculation proc~compute_gmbe compute_gmbe proc~compute_gmbe->proc~print_vibrational_analysis proc~global_coordinator global_coordinator proc~global_coordinator->proc~compute_mbe proc~gmbe_run_distributed gmbe_context_t%gmbe_run_distributed proc~gmbe_run_distributed->proc~gmbe_pie_coordinator proc~gmbe_run_serial gmbe_context_t%gmbe_run_serial proc~gmbe_run_serial->proc~serial_gmbe_pie_processor proc~serial_fragment_processor serial_fragment_processor proc~serial_fragment_processor->proc~compute_mbe interface~global_coordinator global_coordinator interface~global_coordinator->proc~global_coordinator interface~serial_fragment_processor serial_fragment_processor interface~serial_fragment_processor->proc~serial_fragment_processor proc~distributed_unfragmented_hessian distributed_unfragmented_hessian proc~distributed_unfragmented_hessian->interface~hessian_coordinator proc~run_unfragmented_calculation run_unfragmented_calculation proc~run_unfragmented_calculation->interface~unfragmented_calculation interface~distributed_unfragmented_hessian distributed_unfragmented_hessian interface~distributed_unfragmented_hessian->proc~distributed_unfragmented_hessian proc~mbe_run_distributed mbe_context_t%mbe_run_distributed proc~mbe_run_distributed->interface~global_coordinator proc~mbe_run_serial mbe_context_t%mbe_run_serial proc~mbe_run_serial->interface~serial_fragment_processor proc~run_calculation run_calculation proc~run_calculation->proc~run_unfragmented_calculation

Variables

Type Visibility Attributes Name Initial
real(kind=dp), private :: P_pa
real(kind=dp), private :: T
real(kind=dp), private :: V_molar
real(kind=dp), private :: lambda_cubed
real(kind=dp), private :: mass_kg
real(kind=dp), private :: qt

Source Code

   pure subroutine compute_translational_thermo(total_mass, temperature, pressure, E, S, Cv)
      !! Compute translational contributions to thermodynamic properties.
      !!
      !! Uses ideal gas partition function (Sackur-Tetrode equation for entropy).
      !! E_trans = 3/2 * R * T
      !! S_trans = R * [5/2 + ln((2*pi*m*k*T/h^2)^(3/2) * k*T/P)]
      !! Cv_trans = 3/2 * R
      real(dp), intent(in) :: total_mass   !! Total mass in amu
      real(dp), intent(in) :: temperature  !! Temperature in K
      real(dp), intent(in) :: pressure     !! Pressure in atm
      real(dp), intent(out) :: E           !! Thermal energy in Hartree
      real(dp), intent(out) :: S           !! Entropy in cal/(mol*K)
      real(dp), intent(out) :: Cv          !! Heat capacity in cal/(mol*K)

      real(dp) :: mass_kg, T, P_pa
      real(dp) :: lambda_cubed, V_molar, qt

      ! Convert inputs to SI
      mass_kg = total_mass*AMU_TO_KG
      T = temperature
      P_pa = pressure*ATM_TO_PA

      ! Thermal de Broglie wavelength cubed: lambda^3 = (h^2 / (2*pi*m*k*T))^(3/2)
      lambda_cubed = (H_SI*H_SI/(2.0_dp*PI*mass_kg*KB_SI*T))**1.5_dp

      ! Molar volume at given T and P (ideal gas): V = R*T/P = k*T/P per molecule
      V_molar = KB_SI*T/P_pa  ! m^3 per molecule

      ! Translational partition function per molecule
      qt = V_molar/lambda_cubed

      ! Thermal energy: E = 3/2 * R * T
      E = 1.5_dp*R_HARTREE*temperature

      ! Entropy (Sackur-Tetrode): S = R * [5/2 + ln(qt)]
      S = R_CALMOLK*(2.5_dp + log(qt))

      ! Heat capacity: Cv = 3/2 * R
      Cv = 1.5_dp*R_CALMOLK

   end subroutine compute_translational_thermo