mqc_thermochemistry – metalquicha

Computes thermodynamic properties from vibrational frequencies and molecular geometry.

This module implements standard RRHO thermochemistry calculations including: - Zero-point vibrational energy (ZPE) - Translational, rotational, vibrational, and electronic contributions - Thermal corrections to energy, enthalpy, and Gibbs free energy

Default conditions: T = 298.15 K, P = 1 atm Output follows Gaussian-style formatting for compatibility.

Uses

- pic_io
- mqc_physical_constants
- mqc_elements
- pic_lapack_interfaces
- pic_logger
- pic_types
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Variables

Type	Visibility	Attributes		Name		Initial
real(kind=dp),	public,	parameter	::	DEFAULT_PRESSURE	=	1.0_dp	Default pressure in atm
integer,	public,	parameter	::	DEFAULT_SPIN_MULTIPLICITY	=	1	Default spin multiplicity (singlet)
integer,	public,	parameter	::	DEFAULT_SYMMETRY_NUMBER	=	1	Default symmetry number
real(kind=dp),	public,	parameter	::	DEFAULT_TEMPERATURE	=	298.15_dp	Default temperature in Kelvin
real(kind=dp),	private,	parameter	::	IMAG_FREQ_THRESHOLD	=	0.0_dp	Threshold for considering a frequency as imaginary
real(kind=dp),	private,	parameter	::	LINEAR_THRESHOLD	=	1.0e-6_dp	Threshold for considering a moment of inertia as zero (linear molecule detection)

Derived Types

type, public :: thermochemistry_result_t

Container for thermochemistry calculation results

Components

Type	Visibility		Name		Initial
real(kind=dp),	public	::	Cv_rot	=	0.0_dp	Rotational heat capacity
real(kind=dp),	public	::	Cv_trans	=	0.0_dp	Translational heat capacity
real(kind=dp),	public	::	Cv_vib	=	0.0_dp	Vibrational heat capacity
real(kind=dp),	public	::	E_elec	=	0.0_dp	Electronic thermal energy (always 0)
real(kind=dp),	public	::	E_rot	=	0.0_dp	Rotational thermal energy
real(kind=dp),	public	::	E_trans	=	0.0_dp	Translational thermal energy
real(kind=dp),	public	::	E_vib	=	0.0_dp	Vibrational thermal energy (excluding ZPE)
real(kind=dp),	public	::	S_elec	=	0.0_dp	Electronic entropy
real(kind=dp),	public	::	S_rot	=	0.0_dp	Rotational entropy
real(kind=dp),	public	::	S_trans	=	0.0_dp	Translational entropy
real(kind=dp),	public	::	S_vib	=	0.0_dp	Vibrational entropy
logical,	public	::	is_linear	=	.false.	True if molecule is linear
real(kind=dp),	public	::	moments(3)	=	0.0_dp	Principal moments of inertia in amu*Angstrom^2
integer,	public	::	n_imag_freqs	=	0	Number of imaginary frequencies (skipped)
integer,	public	::	n_real_freqs	=	0	Number of real vibrational frequencies
real(kind=dp),	public	::	pressure	=	DEFAULT_PRESSURE	Pressure in atm
real(kind=dp),	public	::	q_rot	=	0.0_dp	Rotational partition function
real(kind=dp),	public	::	q_trans	=	0.0_dp	Translational partition function
real(kind=dp),	public	::	q_vib	=	1.0_dp	Vibrational partition function
real(kind=dp),	public	::	rot_const(3)	=	0.0_dp	Rotational constants in GHz
integer,	public	::	spin_multiplicity	=	DEFAULT_SPIN_MULTIPLICITY	Electronic spin multiplicity
integer,	public	::	symmetry_number	=	DEFAULT_SYMMETRY_NUMBER	Rotational symmetry number
real(kind=dp),	public	::	temperature	=	DEFAULT_TEMPERATURE	Temperature in K
real(kind=dp),	public	::	thermal_correction_energy	=	0.0_dp	E_tot = ZPE + E_trans + E_rot + E_vib
real(kind=dp),	public	::	thermal_correction_enthalpy	=	0.0_dp	H = E_tot + RT
real(kind=dp),	public	::	thermal_correction_gibbs	=	0.0_dp	G = H - TS
real(kind=dp),	public	::	total_mass	=	0.0_dp	Total mass in amu
real(kind=dp),	public	::	zpe_hartree	=	0.0_dp	ZPE in Hartree
real(kind=dp),	public	::	zpe_kcalmol	=	0.0_dp	ZPE in kcal/mol

Subroutines

public pure subroutine compute_electronic_entropy(spin_multiplicity, S_elec)

Compute electronic entropy contribution.

Arguments

Type	Intent	Optional	Attributes		Name
integer,	intent(in)			::	spin_multiplicity	Electronic spin multiplicity (2S+1)
real(kind=dp),	intent(out)			::	S_elec	Electronic entropy in cal/(mol*K)

public subroutine compute_moments_of_inertia(coords, atomic_numbers, n_atoms, center_of_mass, moments, principal_axes, is_linear, total_mass)

Compute the principal moments of inertia and detect linear molecules.

Arguments

Type	Intent		Name
real(kind=dp),	intent(in)	::	coords(:,:)	Atomic coordinates (3, n_atoms) in Bohr
integer,	intent(in)	::	atomic_numbers(:)	Atomic numbers
integer,	intent(in)	::	n_atoms	Number of atoms
real(kind=dp),	intent(out)	::	center_of_mass(3)	Center of mass in Angstrom
real(kind=dp),	intent(out)	::	moments(3)	Principal moments in amu*Angstrom^2
real(kind=dp),	intent(out)	::	principal_axes(3,3)	Principal axis vectors (columns)
logical,	intent(out)	::	is_linear	True if molecule is linear
real(kind=dp),	intent(out)	::	total_mass	Total mass in amu

public pure subroutine compute_rotational_constants(moments, is_linear, rot_const)

Convert moments of inertia to rotational constants in GHz.

Arguments

Type	Intent		Name
real(kind=dp),	intent(in)	::	moments(3)	Moments in amu*Angstrom^2
logical,	intent(in)	::	is_linear	True if linear molecule
real(kind=dp),	intent(out)	::	rot_const(3)	Rotational constants in GHz

public pure subroutine compute_rotational_thermo(moments, temperature, symmetry_number, is_linear, E, S, Cv)

Compute rotational contributions to thermodynamic properties.

Arguments

Type	Intent		Name
real(kind=dp),	intent(in)	::	moments(3)	Principal moments in amu*Angstrom^2
real(kind=dp),	intent(in)	::	temperature	Temperature in K
integer,	intent(in)	::	symmetry_number	Rotational symmetry number
logical,	intent(in)	::	is_linear	True if linear molecule
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)

public subroutine compute_thermochemistry(coords, atomic_numbers, frequencies, n_atoms, n_freqs, result, temperature, pressure, symmetry_number, spin_multiplicity)

Main driver for thermochemistry calculations.

Arguments

Type	Intent	Optional		Name
real(kind=dp),	intent(in)		::	coords(:,:)	Coordinates (3, n_atoms) in Bohr
integer,	intent(in)		::	atomic_numbers(:)	Atomic numbers
real(kind=dp),	intent(in)		::	frequencies(:)	Frequencies in cm^-1
integer,	intent(in)		::	n_atoms	Number of atoms
integer,	intent(in)		::	n_freqs	Number of frequencies
type(thermochemistry_result_t),	intent(out)		::	result	Output results
real(kind=dp),	intent(in),	optional	::	temperature	Temperature in K (default 298.15)
real(kind=dp),	intent(in),	optional	::	pressure	Pressure in atm (default 1.0)
integer,	intent(in),	optional	::	symmetry_number	Symmetry number (default 1)
integer,	intent(in),	optional	::	spin_multiplicity	Spin multiplicity (default 1)

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

Compute translational contributions to thermodynamic properties.

Arguments

Type	Intent		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)

public pure subroutine compute_vibrational_thermo(frequencies, n_freqs, temperature, E, S, Cv)

Compute vibrational contributions to thermodynamic properties.

Arguments

Type	Intent		Name
real(kind=dp),	intent(in)	::	frequencies(:)	Frequencies in cm^-1
integer,	intent(in)	::	n_freqs	Number of frequencies
real(kind=dp),	intent(in)	::	temperature	Temperature in K
real(kind=dp),	intent(out)	::	E	Thermal energy in Hartree (excluding ZPE)
real(kind=dp),	intent(out)	::	S	Entropy in cal/(mol*K)
real(kind=dp),	intent(out)	::	Cv	Heat capacity in cal/(mol*K)

public subroutine compute_zpe(frequencies, n_freqs, n_real, zpe_hartree, zpe_kcalmol)

Compute zero-point vibrational energy from frequencies.

Arguments

Type	Intent		Name
real(kind=dp),	intent(in)	::	frequencies(:)	Vibrational frequencies in cm^-1
integer,	intent(in)	::	n_freqs	Total number of frequencies
integer,	intent(out)	::	n_real	Number of real (positive) frequencies used
real(kind=dp),	intent(out)	::	zpe_hartree	ZPE in Hartree
real(kind=dp),	intent(out)	::	zpe_kcalmol	ZPE in kcal/mol

public subroutine print_thermochemistry(result, electronic_energy, unit)

Print thermochemistry results.

Arguments

Type	Intent	Optional		Name
type(thermochemistry_result_t),	intent(in)		::	result
real(kind=dp),	intent(in)		::	electronic_energy	Electronic energy in Hartree
integer,	intent(in),	optional	::	unit	Output unit (default: stdout)

private pure subroutine compute_partition_functions(total_mass, moments, frequencies, n_freqs, temperature, pressure, sigma, is_linear, q_trans, q_rot, q_vib)

Compute partition functions for translation, rotation, and vibration.

Arguments

Type	Intent		Name
real(kind=dp),	intent(in)	::	total_mass	Total mass in amu
real(kind=dp),	intent(in)	::	moments(3)	Principal moments in amu*Angstrom^2
real(kind=dp),	intent(in)	::	frequencies(:)	Frequencies in cm^-1
integer,	intent(in)	::	n_freqs	Number of frequencies
real(kind=dp),	intent(in)	::	temperature	Temperature in K
real(kind=dp),	intent(in)	::	pressure	Pressure in atm
integer,	intent(in)	::	sigma	Symmetry number
logical,	intent(in)	::	is_linear	True if linear molecule
real(kind=dp),	intent(out)	::	q_trans	Translational partition function
real(kind=dp),	intent(out)	::	q_rot	Rotational partition function
real(kind=dp),	intent(out)	::	q_vib	Vibrational partition function

mqc_thermochemistry Module

Contents

Variables

Derived Types

Subroutines

Uses

Used by

Variables

Derived Types

type, public :: thermochemistry_result_t

Components

Subroutines

public pure subroutine compute_electronic_entropy(spin_multiplicity, S_elec)

Arguments

public subroutine compute_moments_of_inertia(coords, atomic_numbers, n_atoms, center_of_mass, moments, principal_axes, is_linear, total_mass)

Arguments

public pure subroutine compute_rotational_constants(moments, is_linear, rot_const)

Arguments

public pure subroutine compute_rotational_thermo(moments, temperature, symmetry_number, is_linear, E, S, Cv)

Arguments

public subroutine compute_thermochemistry(coords, atomic_numbers, frequencies, n_atoms, n_freqs, result, temperature, pressure, symmetry_number, spin_multiplicity)

Arguments

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

Arguments

public pure subroutine compute_vibrational_thermo(frequencies, n_freqs, temperature, E, S, Cv)

Arguments

public subroutine compute_zpe(frequencies, n_freqs, n_real, zpe_hartree, zpe_kcalmol)

Arguments

public subroutine print_thermochemistry(result, electronic_energy, unit)

Arguments

private pure subroutine compute_partition_functions(total_mass, moments, frequencies, n_freqs, temperature, pressure, sigma, is_linear, q_trans, q_rot, q_vib)

Arguments