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WO2 is Cyanogen Chloride-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is zero-dimensional and consists of two tungsten;dihydrate molecules. W4+ is bonded in a linear geometry to two equivalent O2- atoms. Both W–O bond lengths are 1.80 Å. O2- is bonded in a single-bond geometry to one W4+ atom.
WO2 is Hydrophilite-like structured and crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent W4+ sites. In the first W4+ site, W4+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 50–53°. There are a spread of W–O bond distances ranging from 2.04–2.14 Å. In the second W4+ site, W4+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing WO6 octahedra. The corner-sharing octahedra tilt angles range from 50–53°. There are a spread of W–O bond distances ranging from 2.04–2.14 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three W4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three W4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent W4+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent W4+ atoms.
Al(WO2)2 is Spinel structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent W+2.50+ sites. In the first W+2.50+ site, W+2.50+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six equivalent AlO4 tetrahedra and edges with six WO6 octahedra. There are four shorter (2.24 Å) and two longer (2.34 Å) W–O bond lengths. In the second W+2.50+ site, W+2.50+ is bonded to six equivalent O2- atoms to form WO6 octahedra that share corners with six equivalent AlO4 tetrahedra and edges with six equivalent WO6 octahedra. All W–O bond lengths are 2.19 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with twelve WO6 octahedra. The corner-sharing octahedra tilt angles range from 47–60°. There is one shorter (1.79 Å) and three longer (1.80 Å) Al–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three W+2.50+ and one Al3+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent W+2.50+ and one Al3+ atom.
Mg(WO2)2 is Ilmenite-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are six inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 53–61°. There are three shorter (2.04 Å) and one longer (2.13 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.10–2.21 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four WO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.12–2.16 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share edges with two MgO6 octahedra and edges with four WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.11–2.18 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four equivalent WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.17 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one MgO6 octahedra, and edges with five WO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.24 Å. There are nine inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four WO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.17–2.22 Å. In the second W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six MgO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 39–69°. There are a spread of W–O bond distances ranging from 2.01–2.55 Å. In the third W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent WO4 trigonal pyramids, edges with two MgO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.18 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four MgO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.25 Å. In the fifth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. All W–O bond lengths are 2.02 Å. In the sixth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three MgO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.23 Å. In the seventh W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six MgO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 39–69°. There are a spread of W–O bond distances ranging from 2.01–2.47 Å. In the eighth W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. All W–O bond lengths are 2.02 Å. In the ninth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with three MgO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 45–67°. There are a spread of W–O bond distances ranging from 2.00–2.38 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent W3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to one Mg2+ and three W3+ atoms. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two W3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent W3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four W3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three W3+ atoms. In the eighteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent W3+ atoms.
Ca(WO2)2 is beta indium sulfide-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 54–67°. There are three shorter (2.28 Å) and one longer (2.35 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three equivalent WO4 trigonal pyramids, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.27–2.42 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.31–2.42 Å. In the fourth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three equivalent WO4 trigonal pyramids, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.30–2.41 Å. In the fifth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two WO4 trigonal pyramids, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.22–2.49 Å. In the sixth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with two equivalent WO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, an edgeedge with one CaO6 octahedra, and edges with five WO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.27–2.41 Å. There are twelve inequivalent W3+ sites. In the first W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.21 Å. In the second W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of W–O bond distances ranging from 1.97–2.07 Å. In the third W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent CaO4 tetrahedra, corners with three equivalent WO4 tetrahedra, edges with two CaO6 octahedra, and edges with four WO6 octahedra. There are a spread of W–O bond distances ranging from 2.06–2.27 Å. In the fourth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one WO4 tetrahedra, corners with two equivalent CaO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.18–2.24 Å. In the fifth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four CaO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.24 Å. In the sixth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 39–70°. There are a spread of W–O bond distances ranging from 1.97–2.36 Å. In the seventh W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with two WO4 trigonal pyramids, edges with two equivalent WO6 octahedra, and edges with four CaO6 octahedra. There are a spread of W–O bond distances ranging from 2.00–2.23 Å. In the eighth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with two equivalent WO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.14–2.22 Å. In the ninth W3+ site, W3+ is bonded to four O2- atoms to form WO4 trigonal pyramids that share corners with six CaO6 octahedra and corners with six WO6 octahedra. The corner-sharing octahedra tilt angles range from 43–79°. There are a spread of W–O bond distances ranging from 2.07–2.35 Å. In the tenth W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share a cornercorner with one CaO4 tetrahedra, corners with two equivalent WO4 tetrahedra, corners with two equivalent WO4 trigonal pyramids, edges with three CaO6 octahedra, and edges with three WO6 octahedra. There are a spread of W–O bond distances ranging from 2.15–2.26 Å. In the eleventh W3+ site, W3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of W–O bond distances ranging from 1.97–2.04 Å. In the twelfth W3+ site, W3+ is bonded to four O2- atoms to form distorted WO4 tetrahedra that share corners with three CaO6 octahedra and corners with nine WO6 octahedra. The corner-sharing octahedra tilt angles range from 51–75°. There are a spread of W–O bond distances ranging from 2.04–2.53 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the third O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 tetrahedra that share corners with two OCa2W2 tetrahedra, corners with four OCaW3 trigonal pyramids, and an edgeedge with one OCaW3 tetrahedra. In the fourth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 tetrahedra that share corners with two OCa2W2 tetrahedra, corners with four OCaW3 trigonal pyramids, and an edgeedge with one OCa2W2 tetrahedra. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the ninth O2- site, O2- is bonded in a trigonal non-coplanar geometry to two Ca2+ and one W3+ atom. In the tenth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form OCaW3 trigonal pyramids that share corners with four OCa2W2 tetrahedra and corners with two OCaW3 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one W3+ atom. In the sixteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the seventeenth O2- site, O2- is bonded to two Ca2+ and two W3+ atoms to form distorted OCa2W2 tetrahedra that share corners with two OCa2W2 tetrahedra and corners with four OCaW3 trigonal pyramids. In the eighteenth O2- site, O2- is bonded in a trigonal pyramidal geometry to one Ca2+ and three W3+ atoms. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twentieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two W3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four W3+ atoms. In the twenty-second O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 trigonal pyramids that share corners with four OCa2W2 tetrahedra, corners with two OCaW3 trigonal pyramids, and an edgeedge with one OCaW3 trigonal pyramid. In the twenty-third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the twenty-fourth O2- site, O2- is bonded to one Ca2+ and three W3+ atoms to form distorted OCaW3 trigonal pyramids that share corners with four OCa2W2 tetrahedra, corners with two OCaW3 trigonal pyramids, and an edgeedge with one OCaW3 trigonal pyramid.
Ca(WO2)2 is beta indium sulfide-derived structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three equivalent CaO6 octahedra and corners with nine equivalent WO6 octahedra. The corner-sharing octahedra tilt angles range from 56–65°. There are three shorter (2.27 Å) and one longer (2.32 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three equivalent CaO4 tetrahedra and edges with six equivalent WO6 octahedra. There are three shorter (2.34 Å) and three longer (2.39 Å) Ca–O bond lengths. There are two inequivalent W3+ sites. In the first W3+ site, W3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All W–O bond lengths are 2.02 Å. In the second W3+ site, W3+ is bonded to six O2- atoms to form WO6 octahedra that share corners with three equivalent CaO4 tetrahedra, edges with two equivalent CaO6 octahedra, and edges with four equivalent WO6 octahedra. There are a spread of W–O bond distances ranging from 2.16–2.27 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three W3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent W3+ atoms. In the third O2- site, O2- is bonded to one Ca2+ and three equivalent W3+ atoms to form a mixture of distorted edge and corner-sharing OCaW3 tetrahedra. In the fourth O2- site, O2- is bonded to two Ca2+ and two equivalent W3+ atoms to form distorted OCa2W2 trigonal pyramids that share a cornercorner with one OCaW3 tetrahedra, corners with two equivalent OCa2W2 trigonal pyramids, an edgeedge with one OCaW3 tetrahedra, and edges with two equivalent OCa2W2 trigonal pyramids.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Oxygen fugacity (fO2) controls multivalent phase equilibria and partitioning of redox-sensitive elements, and it is important to understand this thermodynamic parameter in experimental and natural systems. The coexistence of a metal and its oxide at equilibrium constitutes an oxygen buffer which can be used to control or calculate fO2 in high pressure experiments. Application of 1-bar buffers to high pressure conditions can lead to inaccuracies in fO2 calculations because of unconstrained pressure dependencies. Extending fO2 buffers to pressures and temperatures corresponding to the Earth's deep interior requires precise determinations of the difference in volume (Delta) V) between the buffer phases. Synchrotron x-ray diffraction data were obtained using diamond anvil cells (DAC) and a multi anvil press (MAP) to measure unit cell volumes of W and WO2 at pressures and temperatures up to 70 GPa and 2300 K. These data were fitted to Birch-Murnaghan 3rd-order thermal equations of state using a thermal pressure approach; parameters for W are KT = 306 GPa, KT' = 4.06, and αKT = 0.00417 GPa K-1. Two structural phase transitions were observed for WO2 at 4 and 32 GPa with structures in P21/c, Pnma and C2/c space groups. Equations of state were fitted for these phases over their respective pressure ranges yielding the parameters KT = 190, 213, 300 GPa, KT' = 4.24, 5.17, 4 (fixed), and αKT = 0.00506, 0.00419, 0.00467 GPa K-1 for the P21/c, Pnma and C2/c phases, respectively. The W-WO2 buffer (WWO) was extended to high pressure by inverting the W and WO2 equations of state to obtain phase volumes at discrete pressures (1-bar to 100 GPa, 1 GPa increments) along isotherms (300 to 3000K, 100 K increments). The slope of the absolute fO2 of the WWO buffer is positive with increasing temperature up to approximately 70 GPa and is negative above this pressure. The slope is positive along isotherms from 1000 to 3000K with increasing pressure up to at least 100 GPa. The WWO buffer is at a higher fO2 than the IW buffer at pressures lower than 40 GPa, and the magnitude of this difference decreases at higher pressures. This qualitatively indicates an increasingly lithophile character for W at higher pressures. The WWO buffer was quantitatively applied to W metal-silicate partitioning by using the WWO-IW buffer difference in combination with literature data on W metal-silicate partitioning to model the exchange coefficient (KD) for the Fe-W exchange reaction. This approach captures the pressure dependence of W metal-silicate partitioning using the WWO-IW buffer difference and models the activities of the components in the silicate and metallic phases using an expression of the Gibbs excess energy of mixing. Calculation of KD along a peridotite liquidus predicts a decrease in W siderophility at higher pressures that supports the qualitative behavior predicted by the WWO-IW buffer difference, and agrees with findings of others. Comparing the competing effects of temperature and pressure on W metal-silicate partitioning, our results indicate that pressure exerts a greater effect.
The effects of adding Na2MoO4 and Na2WO4 to porous Mo and W electrodes, respectively, on the performance and impedance characteristics of the electrodes in an alkali metal thermoelectric converter (AMTEC) were investigated. It was found that corrosion of the porous electrode by Na2MoO4 or Na2WO4 to form Na2MO3O6 and WO2, respectively, and recrystallization of the Mo or W as the salt evaporates, result in major morphological changes including a loss of columnar structure and a significant increase in porosity. This effect is more pronounced in Na2MoO4/Mo electrodes, due to the lower stability of Na2MoO4.
Astronauts are known to exhibit a variety of immunological alterations during spaceflight including changes in leukocyte distribution and plasma cytokine concentrations, a reduction in T-cell function, and subclinical reactivation of latent herpesviruses. These alterations are most likely due to mission-associated stressors including circadian misalignment, microgravity, isolation, altered nutrition, and increased exposure to cosmic radiation. Some of these stressors may also occur in terrestrial situations. This study sought to determine if crewmembers performing overwinter deployment at Palmer Station, Antarctica displayed similar immune alterations. The larger goal was to validate a ground analog suitable for the evaluation of countermeasures designed to protect astronauts during future deep space missions. For this pilot study, plasma, saliva, hair, and health surveys were collected from Palmer Station, Antarctica winterover participants at baseline, and at five overwinter timepoints. Twenty-six subjects consented to participate over the course of two seasons. Initial sample processing was performed at Palmer, and eventually stabilized samples were returned to the Johnson Space Center for analysis. A white blood cell differential was performed (real time) using a fingerstick blood sample to determine alterations in basic leukocyte subsets throughout the winterover. Plasma and saliva samples were analyzed for 30 and 13 cytokines, respectively. Saliva was analyzed for cortisol concentration and three latent herpesviruses (DNA by qPCR), EBV, HSV1, and VZV. Hair samples were analyzed for several hormones, as a measure of stress over prolonged periods of time. Voluntary surveys related to general health and adverse clinical events were distributed to participants. It is noteworthy that due to logistical constraints due to COVID-19, the baseline samples for each season were collected in Punta Arenas, Chile, after long international travel and during isolation. Therefore, the palmer pre mission samples may not reflect a true normal ‘baseline’. Minimal alterations were observed in leukocyte distribution during overwinter. The mean percentage of monocyte concentration elevated at one timepoint. Plasma G-CSF, IL1RA, MCP-1, MIP-1β, TNFα and VEGF were decreased during at least one overwinter timepoint, whereas RANTES was significantly increased. No statistically significant changes were observed in mean saliva cytokine concentrations. Salivary cortisol was substantially elevated throughout the entire winterover compared to baseline. Compared to shedding levels observed in healthy controls (23%), the percentage of participants who shed EBV was higher throughout all winterover timepoints (52-60%). Five subjects shed HSV1 during at least one timepoint throughout the season compared to no subjects shedding during pre-deployment. Finally, VZV reactivation, common in astronauts but exceptionally rare in ground-based stress analogs, was observed in one subject during pre-deployment and a different subject at WO2 and WO3. These pilot data, somewhat influenced by the COVID-19 situation, do suggest that participants at Palmer Station do undergo immunological alterations similar to, but likely in reduced magnitude, as those observed in astronauts. We suggest that overwinter at Palmer Station may be suitable test analog for spaceflight biomedical countermeasures designed to mitigate clinical risks for deep space missions.