def compute_volume(self, pressure=0., temperature=0.):
"""
Computes the unit cell volume of the material.
It can compute volumes at different pressures and temperatures.
Keywords:
pressure:
The pressure in GPa. If not present then the pressure is
assumed to be 0.
temperature:
The temperature in K. If not present or zero, then the
temperature is assumed to be 298K, i.e. room temperature.
Procedure:
This procedure computes the unit cell volume. It starts with the
volume read from the JCPDS file or computed from the zero-pressure,
room temperature lattice constants. It does the following:
1) Corrects K0 for temperature if DK0DT is non-zero.
2) Computes volume at zero-pressure and the specified temperature
if ALPHAT0 is non-zero.
3) Computes the volume at the specified pressure if K0 is non-zero.
The routine uses the IDL function FX_ROOT to solve the third
order Birch-Murnaghan equation of state.
Example:
Compute the unit cell volume of alumina at 100 GPa and 2500 K.
j = jcpds()
j.read_file('alumina.jcpds')
j.compute_volume(100, 2500)
"""
# Assume 0 K really means room T
if (temperature == 0): temperature = 298.
# Compute values of K0, K0P and alphat at this temperature
self.alphat = self.alphat0 + self.dalphadt * (temperature - 298.)
self.k0p = self.k0p0 + self.dk0pdt * (temperature - 298.)
if (pressure == 0.):
self.v = self.v0 * (1 + self.alphat * (temperature - 298.))
else:
if (self.k0 <= 0.):
print 'K0 is zero, computing zero pressure volume'
self.v = self.v0
else:
self.mod_pressure = pressure - \
self.alphat*self.k0*(temperature-298.)
v0_v = CARSMath.newton(self.bm3_inverse, 1.)
self.v = self.v0 / v0_v
def compute_volume(self, pressure=0., temperature=0.):
"""
Computes the unit cell volume of the material.
It can compute volumes at different pressures and temperatures.
Keywords:
pressure:
The pressure in GPa. If not present then the pressure is
assumed to be 0.
temperature:
The temperature in K. If not present or zero, then the
temperature is assumed to be 298K, i.e. room temperature.
Procedure:
This procedure computes the unit cell volume. It starts with the
volume read from the JCPDS file or computed from the zero-pressure,
room temperature lattice constants. It does the following:
1) Corrects K0 for temperature if DK0DT is non-zero.
2) Computes volume at zero-pressure and the specified temperature
if ALPHAT0 is non-zero.
3) Computes the volume at the specified pressure if K0 is non-zero.
The routine uses the IDL function FX_ROOT to solve the third
order Birch-Murnaghan equation of state.
Example:
Compute the unit cell volume of alumina at 100 GPa and 2500 K.
j = jcpds()
j.read_file('alumina.jcpds')
j.compute_volume(100, 2500)
"""
# Assume 0 K really means room T
if (temperature == 0): temperature=298.
# Compute values of K0, K0P and alphat at this temperature
self.alphat = self.alphat0 + self.dalphadt*(temperature-298.)
self.k0p = self.k0p0 + self.dk0pdt*(temperature-298.)
if (pressure == 0.):
self.v = self.v0 * (1 + self.alphat*(temperature-298.))
else:
if (self.k0 <= 0.):
print 'K0 is zero, computing zero pressure volume'
self.v = self.v0
else:
self.mod_pressure = pressure - \
self.alphat*self.k0*(temperature-298.)
v0_v = CARSMath.newton(self.bm3_inverse, 1.)
self.v = self.v0/v0_v
